From 83df58a040d02f28b79f5520f3b1e1047aa2af6d Mon Sep 17 00:00:00 2001
From: Chris Andreae <chris@bibo.com.ph>
Date: Thu, 13 Sep 2018 16:20:00 +0900
Subject: [PATCH] iKnow ViewModels 3.0.0

Removes support for explicit shared on associations. ViewModels are now
explicitly declared as either roots or nested children.

Removes support for `optional` associations and dynamic prune/include in
seralization. Associations may now be `external`. External associations are
never (de)serialized as part of the parent, and may only be manipulated
externally with `AssociationManipulation`.

Fixes #100
---
 iknow_view_models.gemspec                     |   2 +-
 lib/iknow_view_models/version.rb              |   2 +-
 lib/view_model.rb                             |  25 +-
 lib/view_model/active_record.rb               | 168 ++--
 .../active_record/association_data.rb         | 298 ++++--
 .../active_record/association_manipulation.rb |  34 +-
 lib/view_model/active_record/cache.rb         |   4 +-
 .../active_record/cache/cacheable_view.rb     |   4 +-
 lib/view_model/active_record/cloner.rb        |  22 +-
 lib/view_model/active_record/controller.rb    |   2 -
 .../active_record/update_context.rb           |  24 +-
 lib/view_model/active_record/update_data.rb   |  88 +-
 .../active_record/update_operation.rb         | 418 +++++----
 lib/view_model/active_record/visitor.rb       |  15 +-
 lib/view_model/changes.rb                     |  40 +-
 lib/view_model/config.rb                      |   8 +-
 lib/view_model/deserialization_error.rb       |  31 +
 lib/view_model/deserialize_context.rb         |   8 +-
 lib/view_model/record.rb                      |  68 +-
 lib/view_model/record/attribute_data.rb       |  17 +-
 lib/view_model/serialize_context.rb           |  65 +-
 shell.nix                                     |   2 +-
 test/helpers/arvm_test_utilities.rb           |   6 +
 test/helpers/controller_test_helpers.rb       |   8 +-
 test/helpers/viewmodel_spec_helpers.rb        | 115 +--
 test/unit/view_model/access_control_test.rb   | 125 ++-
 .../active_record/belongs_to_test.rb          | 288 +++---
 .../view_model/active_record/cache_test.rb    |   5 +-
 .../view_model/active_record/cloner_test.rb   |   2 +-
 .../active_record/controller_test.rb          |  20 +-
 .../view_model/active_record/has_many_test.rb | 856 +++++++++++-------
 .../has_many_through_poly_test.rb             |  27 +-
 .../active_record/has_many_through_test.rb    |  73 +-
 .../view_model/active_record/has_one_test.rb  | 423 ++++++---
 .../optional_attribute_view_test.rb           |  58 --
 .../view_model/active_record/poly_test.rb     |   1 -
 .../view_model/active_record/shared_test.rb   |  60 +-
 .../view_model/active_record/version_test.rb  |   5 +-
 test/unit/view_model/active_record_test.rb    |  68 +-
 test/unit/view_model/callbacks_test.rb        |   1 +
 test/unit/view_model/record_test.rb           |  32 -
 .../unit/view_model/traversal_context_test.rb |  25 +-
 42 files changed, 1998 insertions(+), 1545 deletions(-)
 delete mode 100644 test/unit/view_model/active_record/optional_attribute_view_test.rb

diff --git a/iknow_view_models.gemspec b/iknow_view_models.gemspec
index 51ba7915..7496ea70 100644
--- a/iknow_view_models.gemspec
+++ b/iknow_view_models.gemspec
@@ -24,7 +24,7 @@ Gem::Specification.new do |spec|
   spec.add_dependency "activesupport", ">= 5.0"
 
   spec.add_dependency "acts_as_manual_list"
-  spec.add_dependency "deep_preloader"
+  spec.add_dependency "deep_preloader", ">= 1.0.1"
   spec.add_dependency "iknow_cache"
   spec.add_dependency "iknow_params", "~> 2.2.0"
   spec.add_dependency "safe_values"
diff --git a/lib/iknow_view_models/version.rb b/lib/iknow_view_models/version.rb
index 55ce3a17..128a1919 100644
--- a/lib/iknow_view_models/version.rb
+++ b/lib/iknow_view_models/version.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module IknowViewModels
-  VERSION = '2.8.9'
+  VERSION = '3.0.0'
 end
diff --git a/lib/view_model.rb b/lib/view_model.rb
index d73ac3ea..0b6536ed 100644
--- a/lib/view_model.rb
+++ b/lib/view_model.rb
@@ -20,6 +20,7 @@ class << self
     attr_accessor :_attributes
     attr_accessor :schema_version
     attr_reader   :view_aliases
+    attr_writer   :view_name
 
     def inherited(subclass)
       subclass.initialize_as_viewmodel
@@ -41,15 +42,23 @@ def view_name
         end
     end
 
-    def view_name=(name)
-      @view_name = name
-    end
-
     def add_view_alias(as)
       view_aliases << as
       ViewModel::Registry.register(self, as: as)
     end
 
+    # ViewModels are either roots or children. Root viewmodels may be
+    # (de)serialized directly, whereas child viewmodels are always nested within
+    # their parent. Associations to root viewmodel types always use indirect
+    # references.
+    def root?
+      false
+    end
+
+    def root!
+      define_singleton_method(:root?) { true }
+    end
+
     # ViewModels are typically going to be pretty simple structures. Make it a
     # bit easier to define them: attributes specified this way are given
     # accessors and assigned in order by the default constructor.
@@ -59,7 +68,7 @@ def attributes(*attrs, **args)
 
     def attribute(attr, **_args)
       unless attr.is_a?(Symbol)
-        raise ArgumentError.new("ViewModel attributes must be symbols")
+        raise ArgumentError.new('ViewModel attributes must be symbols')
       end
 
       attr_accessor attr
@@ -116,7 +125,7 @@ def is_update_hash?(hash)
     # If this viewmodel represents an AR model, what associations does it make
     # use of? Returns a includes spec appropriate for DeepPreloader, either as
     # AR-style nested hashes or DeepPreloader::Spec.
-    def eager_includes(serialize_context: new_serialize_context, include_shared: true)
+    def eager_includes(serialize_context: new_serialize_context, include_referenced: true)
       {}
     end
 
@@ -225,10 +234,10 @@ def accepts_schema_version?(schema_version)
       schema_version == self.schema_version
     end
 
-    def preload_for_serialization(viewmodels, serialize_context: new_serialize_context, include_shared: true, lock: nil)
+    def preload_for_serialization(viewmodels, serialize_context: new_serialize_context, include_referenced: true, lock: nil)
       Array.wrap(viewmodels).group_by(&:class).each do |type, views|
         DeepPreloader.preload(views.map(&:model),
-                              type.eager_includes(serialize_context: serialize_context, include_shared: include_shared),
+                              type.eager_includes(serialize_context: serialize_context, include_referenced: include_referenced),
                               lock: lock)
       end
     end
diff --git a/lib/view_model/active_record.rb b/lib/view_model/active_record.rb
index bee9f38a..4f9e47d0 100644
--- a/lib/view_model/active_record.rb
+++ b/lib/view_model/active_record.rb
@@ -63,42 +63,58 @@ def _list_member?
       _list_attribute_name.present?
     end
 
-    # Specifies an association from the model to be recursively serialized using
-    # another viewmodel. If the target viewmodel is not specified, attempt to
-    # locate a default viewmodel based on the name of the associated model.
-    # TODO document harder
+    # Adds an association from the model to this viewmodel. The associated model
+    # will be recursively (de)serialized by its own viewmodel type, which will
+    # be inferred from the model name, or may be explicitly specified.
+    #
+    # An association to a root viewmodel type will be serialized with an
+    # indirect reference, while a child viewmodel type will be directly nested.
+    #
+    # - +as+ sets the name of the association in the viewmodel
+    #
+    # - +viewmodel+, +viewmodels+ specifies the viewmodel(s) to use for the
+    #   association
+    #
+    # - +external+ indicates an association external to the view. Externalized
+    #   associations are not included in (de)serializations of the parent, and
+    #   must be independently manipulated using `AssociationManipulation`.
+    #   External associations may only be made to root viewmodels.
+    #
     # - +through+ names an ActiveRecord association that will be used like an
     #   ActiveRecord +has_many:through:+.
+    #
     # - +through_order_attr+ the through model is ordered by the given attribute
     #   (only applies to when +through+ is set).
     def association(association_name,
+                    as: nil,
                     viewmodel: nil,
                     viewmodels: nil,
-                    shared: false,
-                    optional: false,
+                    external: false,
+                    read_only: false,
                     through: nil,
-                    through_order_attr: nil,
-                    as: nil)
-
-      if through
-        model_association_name = through
-        through_to             = association_name
-      else
-        model_association_name = association_name
-        through_to             = nil
-      end
+                    through_order_attr: nil)
 
       vm_association_name = (as || association_name).to_s
 
-      reflection = model_class.reflect_on_association(model_association_name)
-
-      if reflection.nil?
-        raise ArgumentError.new("Association #{model_association_name} not found in #{model_class.name} model")
+      if through
+        direct_association_name   = through
+        indirect_association_name = association_name
+      else
+        direct_association_name   = association_name
+        indirect_association_name = nil
       end
 
-      viewmodel_spec = viewmodel || viewmodels
+      target_viewmodels = Array.wrap(viewmodel || viewmodels)
 
-      association_data = AssociationData.new(vm_association_name, reflection, viewmodel_spec, shared, optional, through_to, through_order_attr)
+      association_data = AssociationData.new(
+        owner:                     self,
+        association_name:          vm_association_name,
+        direct_association_name:   direct_association_name,
+        indirect_association_name: indirect_association_name,
+        target_viewmodels:         target_viewmodels,
+        external:                  external,
+        read_only:                 read_only,
+        through_order_attr:        through_order_attr)
 
       _members[vm_association_name] = association_data
 
@@ -108,21 +124,7 @@ def association(association_name,
         end
 
         define_method :"serialize_#{vm_association_name}" do |json, serialize_context: self.class.new_serialize_context|
-          associated = self.public_send(vm_association_name)
-          json.set! vm_association_name do
-            case
-            when associated.nil?
-              json.null!
-            when association_data.through?
-              json.array!(associated) do |through_target|
-                self.class.serialize_as_reference(through_target, json, serialize_context: serialize_context)
-              end
-            when shared
-              self.class.serialize_as_reference(associated, json, serialize_context: serialize_context)
-            else
-              self.class.serialize(associated, json, serialize_context: serialize_context)
-            end
-          end
+          _serialize_association(vm_association_name, json, serialize_context: serialize_context)
         end
       end
     end
@@ -171,11 +173,6 @@ def deserialize_from_view(subtree_hash_or_hashes, references: {}, deserialize_co
         ViewModel::Utils.wrap_one_or_many(subtree_hash_or_hashes) do |subtree_hashes|
           root_update_data, referenced_update_data = UpdateData.parse_hashes(subtree_hashes, references)
 
-          # Provide information about what was updated
-          deserialize_context.updated_associations = root_update_data
-                                                       .map { |upd| upd.updated_associations }
-                                                       .inject({}) { |acc, assocs| acc.deep_merge(assocs) }
-
           _updated_viewmodels =
             UpdateContext
               .build!(root_update_data, referenced_update_data, root_type: self)
@@ -184,27 +181,18 @@ def deserialize_from_view(subtree_hash_or_hashes, references: {}, deserialize_co
       end
     end
 
-    def eager_includes(serialize_context: new_serialize_context, include_shared: true)
-      # When serializing, we need to (recursively) include all intrinsic
-      # associations and also those optional (incl. shared) associations
-      # specified in the serialize_context.
-
-      # when deserializing, we start with intrinsic non-shared associations. We
-      # then traverse the structure of the tree to deserialize to map out which
-      # optional or shared associations are used from each type. We then explore
-      # from the root type to build an preload specification that will include
-      # them all. (We can subsequently use this same structure to build a
-      # serialization context featuring the same associations.)
-
+    # Constructs a preload specification of the required models for
+    # serializing/deserializing this view.
+    def eager_includes(serialize_context: new_serialize_context, include_referenced: true)
       association_specs = {}
       _members.each do |assoc_name, association_data|
         next unless association_data.is_a?(AssociationData)
-        next unless serialize_context.includes_member?(assoc_name, !association_data.optional?)
+        next if association_data.external?
 
         child_context =
           if self.synthetic
             serialize_context
-          elsif association_data.shared?
+          elsif association_data.referenced?
             serialize_context.for_references
           else
             serialize_context.for_child(nil, association_name: assoc_name)
@@ -213,22 +201,22 @@ def eager_includes(serialize_context: new_serialize_context, include_shared: tru
         case
         when association_data.through?
           viewmodel = association_data.direct_viewmodel
-          children = viewmodel.eager_includes(serialize_context: child_context, include_shared: include_shared)
+          children = viewmodel.eager_includes(serialize_context: child_context, include_referenced: include_referenced)
 
-        when !include_shared && association_data.shared?
-          children = nil # Load up to the shared model, but no further
+        when !include_referenced && association_data.referenced?
+          children = nil # Load up to the root viewmodel, but no further
 
         when association_data.polymorphic?
           children_by_klass = {}
           association_data.viewmodel_classes.each do |vm_class|
             klass = vm_class.model_class.name
-            children_by_klass[klass] = vm_class.eager_includes(serialize_context: child_context, include_shared: include_shared)
+            children_by_klass[klass] = vm_class.eager_includes(serialize_context: child_context, include_referenced: include_referenced)
           end
           children = DeepPreloader::PolymorphicSpec.new(children_by_klass)
 
         else
           viewmodel = association_data.viewmodel_class
-          children = viewmodel.eager_includes(serialize_context: child_context, include_shared: include_shared)
+          children = viewmodel.eager_includes(serialize_context: child_context, include_referenced: include_referenced)
         end
 
         association_specs[association_data.direct_reflection.name.to_s] = children
@@ -236,26 +224,26 @@ def eager_includes(serialize_context: new_serialize_context, include_shared: tru
       DeepPreloader::Spec.new(association_specs)
     end
 
-    def dependent_viewmodels(seen = Set.new, include_shared: true)
+    def dependent_viewmodels(seen = Set.new, include_referenced: true)
       return if seen.include?(self)
 
       seen << self
 
       _members.each_value do |data|
         next unless data.is_a?(AssociationData)
-        next unless include_shared || !data.shared?
+        next unless include_referenced || !data.referenced?
         data.viewmodel_classes.each do |vm|
-          vm.dependent_viewmodels(seen, include_shared: include_shared)
+          vm.dependent_viewmodels(seen, include_referenced: include_referenced)
         end
       end
 
       seen
     end
 
-    def deep_schema_version(include_shared: true)
-      (@deep_schema_version ||= {})[include_shared] ||=
+    def deep_schema_version(include_referenced: true)
+      (@deep_schema_version ||= {})[include_referenced] ||=
         begin
-          dependent_viewmodels(include_shared: include_shared).each_with_object({}) do |view, h|
+          dependent_viewmodels(include_referenced: include_referenced).each_with_object({}) do |view, h|
             h[view.view_name] = view.schema_version
           end
         end
@@ -270,6 +258,7 @@ def cacheable!(**opts)
     def _association_data(association_name)
       association_data = self._members[association_name.to_s]
       raise ArgumentError.new("Invalid association '#{association_name}'") unless association_data.is_a?(AssociationData)
+
       association_data
     end
   end
@@ -282,7 +271,7 @@ def initialize(*)
 
   def serialize_members(json, serialize_context: self.class.new_serialize_context)
     self.class._members.each do |member_name, member_data|
-      next unless serialize_context.includes_member?(member_name, !member_data.optional?)
+      next if member_data.association? && member_data.external?
 
       member_context =
         case member_data
@@ -309,6 +298,13 @@ def destroy!(deserialize_context: self.class.new_deserialize_context)
 
   def association_changed!(association_name)
     association_name = association_name.to_s
+
+    association_data = self.class._association_data(association_name)
+
+    if association_data.read_only?
+      raise ViewModel::DeserializationError::ReadOnlyAssociation.new(association_name, blame_reference)
+    end
+
     unless @changed_associations.include?(association_name)
       @changed_associations << association_name
     end
@@ -321,10 +317,12 @@ def associations_changed?
   # Additionally pass `changed_associations` while constructing changes.
   def changes
     ViewModel::Changes.new(
-      new:                  new_model?,
-      changed_attributes:   changed_attributes,
-      changed_associations: changed_associations,
-      changed_children:     changed_children?)
+      new:                         new_model?,
+      changed_attributes:          changed_attributes,
+      changed_associations:        changed_associations,
+      changed_nested_children:     changed_nested_children?,
+      changed_referenced_children: changed_referenced_children?,
+    )
   end
 
   def clear_changes!
@@ -365,14 +363,36 @@ def _read_association(association_name)
     end
   end
 
+  def _serialize_association(association_name, json, serialize_context:)
+    associated = self.public_send(association_name)
+    association_data = self.class._association_data(association_name)
+
+    json.set! association_name do
+      case
+      when associated.nil?
+        json.null!
+      when association_data.referenced?
+        if association_data.collection?
+          json.array!(associated) do |target|
+            self.class.serialize_as_reference(target, json, serialize_context: serialize_context)
+          end
+        else
+          self.class.serialize_as_reference(associated, json, serialize_context: serialize_context)
+        end
+      else
+        self.class.serialize(associated, json, serialize_context: serialize_context)
+      end
+    end
+  end
+
   def context_for_child(member_name, context:)
     # Synthetic viewmodels don't exist as far as the traversal context is
     # concerned: pass through the child context received from the parent
     return context if self.class.synthetic
 
-    # Shared associations start a new tree
+    # associations to roots start a new tree
     member_data = self.class._members[member_name.to_s]
-    if member_data.is_a?(AssociationData) && member_data.shared?
+    if member_data.association? && member_data.referenced?
       return context.for_references
     end
 
diff --git a/lib/view_model/active_record/association_data.rb b/lib/view_model/active_record/association_data.rb
index 258cf92d..5cc25a09 100644
--- a/lib/view_model/active_record/association_data.rb
+++ b/lib/view_model/active_record/association_data.rb
@@ -1,95 +1,137 @@
 # frozen_string_literal: true
 
-# TODO consider rephrase scope for consistency
 class ViewModel::ActiveRecord::AssociationData
-  attr_reader :direct_reflection, :association_name
-
-  def initialize(association_name, direct_reflection, viewmodel_classes, shared, optional, through_to, through_order_attr)
-    @association_name   = association_name
-    @direct_reflection  = direct_reflection
-    @shared             = shared
-    @optional           = optional
-    @through_to         = through_to
-    @through_order_attr = through_order_attr
-
-    if viewmodel_classes
-      @viewmodel_classes = Array.wrap(viewmodel_classes).map! do |v|
-        case v
-        when String, Symbol
-          ViewModel::Registry.for_view_name(v.to_s)
-        when Class
-          v
+  class InvalidAssociation < RuntimeError; end
+
+  attr_reader :association_name, :direct_reflection
+
+  def initialize(owner:,
+                 association_name:,
+                 direct_association_name:,
+                 indirect_association_name:,
+                 target_viewmodels:,
+                 external:,
+                 through_order_attr:,
+                 read_only:)
+    @association_name = association_name
+
+    @direct_reflection = owner.model_class.reflect_on_association(direct_association_name)
+    if @direct_reflection.nil?
+      raise InvalidAssociation.new("Association '#{direct_association_name}' not found in model '#{model_class.name}'")
+    end
+
+    @indirect_association_name = indirect_association_name
+
+    @read_only           = read_only
+    @external            = external
+    @through_order_attr  = through_order_attr
+    @target_viewmodels   = target_viewmodels
+
+    # Target models/reflections/viewmodels are lazily evaluated so that we can
+    # safely express cycles.
+    @initialized         = false
+    @mutex               = Mutex.new
+  end
+
+  def lazy_initialize!
+    @mutex.synchronize do
+      return if @initialized
+
+      if through?
+        intermediate_model   = @direct_reflection.klass
+        @indirect_reflection = load_indirect_reflection(intermediate_model, @indirect_association_name)
+        target_reflection    = @indirect_reflection
+      else
+        target_reflection    = @direct_reflection
+      end
+
+      @viewmodel_classes =
+        if @target_viewmodels.present?
+          # Explicitly named
+          @target_viewmodels.map { |v| resolve_viewmodel_class(v) }
         else
-          raise ArgumentError.new("Invalid viewmodel class: #{v.inspect}")
+          # Infer name from name of model
+          if target_reflection.polymorphic?
+            raise InvalidAssociation.new(
+                    'Cannot automatically infer target viewmodels from polymorphic association')
+          end
+          infer_viewmodel_class(target_reflection.klass)
         end
+
+      @referenced = @viewmodel_classes.first.root?
+
+      # Non-referenced viewmodels must be owned. For referenced viewmodels, we
+      # own it if it points to us. Through associations aren't considered
+      # `owned?`: while we do own the implicit direct viewmodel, we don't own
+      # the target of the association.
+      @owned = !@referenced || (target_reflection.macro != :belongs_to)
+
+      unless @viewmodel_classes.all? { |v| v.root? == @referenced }
+        raise InvalidAssociation.new('Invalid association target: mixed root and non-root viewmodels')
       end
-    end
 
-    if through?
-      # Through associations must always be an owned direct association to a
-      # shared indirect target. We expect the user to set shared: true to
-      # express the ownership of the indirect target, but this direct
-      # association to the intermediate is in fact owned. This ownership
-      # property isn't directly used anywhere: the synthetic intermediate
-      # viewmodel is only used in the deserialization update operations, which
-      # directly understands the semantics of through associations.
-      raise ArgumentError.new("Through associations must be to a shared target") unless @shared
-      raise ArgumentError.new("Through associations must be `has_many`") unless direct_reflection.macro == :has_many
-    end
-  end
+      if external? && !@referenced
+        raise InvalidAssociation.new('External associations must be to root viewmodels')
+      end
 
-  # reflection for the target of this association: indirect if through, direct otherwise
-  def target_reflection
-    if through?
-      indirect_reflection
-    else
-      direct_reflection
+      if through?
+        unless @referenced
+          raise InvalidAssociation.new('Through associations must be to root viewmodels')
+        end
+
+        @direct_viewmodel = build_direct_viewmodel(@direct_reflection, @indirect_reflection,
+                                                   @viewmodel_classes, @through_order_attr)
+      end
+
+      @initialized = true
     end
   end
 
-  def polymorphic?
-    target_reflection.polymorphic?
+  def association?
+    true
   end
 
-  def viewmodel_classes
-    # If we weren't given explicit viewmodel classes, try to work out from the
-    # names. This should work unless the association is polymorphic.
-    @viewmodel_classes ||=
-      begin
-        model_class = target_reflection.klass
-        if model_class.nil?
-          raise "Couldn't derive target class for association '#{target_reflection.name}"
-        end
-        inferred_view_name = ViewModel::Registry.default_view_name(model_class.name)
-        viewmodel_class = ViewModel::Registry.for_view_name(inferred_view_name) # TODO: improve error message to show it's looking for default name
-        [viewmodel_class]
-      end
+  def referenced?
+    lazy_initialize! unless @initialized
+    @referenced
   end
 
-  private def model_to_viewmodel
-    @model_to_viewmodel ||= viewmodel_classes.each_with_object({}) do |vm, h|
-      h[vm.model_class] = vm
-    end
+  def nested?
+    !referenced?
   end
 
-  private def name_to_viewmodel
-    @name_to_viewmodel ||= viewmodel_classes.each_with_object({}) do |vm, h|
-      h[vm.view_name] = vm
-      vm.view_aliases.each do |view_alias|
-        h[view_alias] = vm
-      end
-    end
+  def owned?
+    lazy_initialize! unless @initialized
+    @owned
   end
 
   def shared?
-    @shared
+    !owned?
+  end
+
+  def external?
+    @external
+  end
+
+  def read_only?
+    @read_only
+  end
+
+  # reflection for the target of this association: indirect if through, direct otherwise
+  def target_reflection
+    if through?
+      indirect_reflection
+    else
+      direct_reflection
+    end
   end
 
-  def optional?
-    @optional
+  def polymorphic?
+    target_reflection.polymorphic?
   end
 
-  def pointer_location # TODO name
+  # The side of the immediate association that holds the pointer.
+  def pointer_location
     case direct_reflection.macro
     when :belongs_to
       :local
@@ -98,6 +140,24 @@ def pointer_location # TODO name
     end
   end
 
+  def indirect_reflection
+    lazy_initialize! unless @initialized
+    @indirect_reflection
+  end
+
+  def direct_reflection_inverse(foreign_class = nil)
+    if direct_reflection.polymorphic?
+      direct_reflection.polymorphic_inverse_of(foreign_class)
+    else
+      direct_reflection.inverse_of
+    end
+  end
+
+  def viewmodel_classes
+    lazy_initialize! unless @initialized
+    @viewmodel_classes
+  end
+
   def viewmodel_class_for_model(model_class)
     model_to_viewmodel[model_class]
   end
@@ -132,47 +192,101 @@ def viewmodel_class
     unless viewmodel_classes.size == 1
       raise ArgumentError.new("More than one possible class for association '#{target_reflection.name}'")
     end
+
     viewmodel_classes.first
   end
 
   def through?
-    @through_to.present?
+    @indirect_association_name.present?
   end
 
   def direct_viewmodel
-    @direct_viewmodel ||= begin
-      raise 'not a through association' unless through?
+    raise ArgumentError.new('not a through association') unless through?
+    lazy_initialize! unless @initialized
+    @direct_viewmodel
+  end
+
+  def collection?
+    through? || direct_reflection.collection?
+  end
 
-      # Join table viewmodel class
+  def indirect_association_data
+    direct_viewmodel._association_data(indirect_reflection.name)
+  end
 
-      # For A has_many B through T; where this association is defined on A
+  private
 
-      # Copy into scope for new class block
-      direct_reflection   = self.direct_reflection    # A -> T
-      indirect_reflection = self.indirect_reflection  # T -> B
-      through_order_attr  = @through_order_attr
-      viewmodel_classes   = self.viewmodel_classes
+  # Through associations must always be to a root viewmodel, via an owned
+  # has_many association to an intermediate model. A synthetic viewmodel is
+  # created to represent this intermediate, but is used only internally by the
+  # deserialization update operations, which directly understands the semantics
+  # of through associations.
+  def load_indirect_reflection(intermediate_model, indirect_association_name)
+    indirect_reflection =
+      intermediate_model.reflect_on_association(ActiveSupport::Inflector.singularize(indirect_association_name))
 
-      Class.new(ViewModel::ActiveRecord) do
-        self.synthetic = true
-        self.model_class = direct_reflection.klass
-        self.view_name = direct_reflection.klass.name
-        association indirect_reflection.name, shared: true, optional: false, viewmodels: viewmodel_classes
-        acts_as_list through_order_attr if through_order_attr
-      end
+    if indirect_reflection.nil?
+      raise InvalidAssociation.new(
+              "Indirect association '#{@indirect_association_name}' not found in "\
+              "intermediate model '#{intermediate_model.name}'")
+    end
+
+    unless direct_reflection.macro == :has_many
+      raise InvalidAssociation.new('Through associations must be `has_many`')
     end
+
+    indirect_reflection
   end
 
-  def indirect_reflection
-    @indirect_reflection ||=
-      direct_reflection.klass.reflect_on_association(ActiveSupport::Inflector.singularize(@through_to))
+  def build_direct_viewmodel(direct_reflection, indirect_reflection, viewmodel_classes, through_order_attr)
+    # Join table viewmodel class. For A has_many B through T; where this association is defined on A
+    # direct_reflection   = A -> T
+    # indirect_reflection = T -> B
+
+    Class.new(ViewModel::ActiveRecord) do
+      self.synthetic = true
+      self.model_class = direct_reflection.klass
+      self.view_name = direct_reflection.klass.name
+      association indirect_reflection.name, viewmodels: viewmodel_classes
+      acts_as_list through_order_attr if through_order_attr
+    end
   end
 
-  def collection?
-    through? || direct_reflection.collection?
+  def resolve_viewmodel_class(v)
+    case v
+    when String, Symbol
+      ViewModel::Registry.for_view_name(v.to_s)
+    when Class
+      v
+    else
+      raise InvalidAssociation.new("Invalid viewmodel class: #{v.inspect}")
+    end
   end
 
-  def indirect_association_data
-    direct_viewmodel._association_data(indirect_reflection.name)
+  def infer_viewmodel_class(model_class)
+    # If we weren't given explicit viewmodel classes, try to work out from the
+    # names. This should work unless the association is polymorphic.
+    if model_class.nil?
+      raise InvalidAssociation.new("Couldn't derive target class for model association '#{target_reflection.name}'")
+    end
+
+    inferred_view_name = ViewModel::Registry.default_view_name(model_class.name)
+    viewmodel_class = ViewModel::Registry.for_view_name(inferred_view_name) # TODO: improve error message to show it's looking for default name
+    [viewmodel_class]
+  end
+
+  def model_to_viewmodel
+    @model_to_viewmodel ||= viewmodel_classes.each_with_object({}) do |vm, h|
+      h[vm.model_class] = vm
+    end
+  end
+
+  def name_to_viewmodel
+    @name_to_viewmodel ||= viewmodel_classes.each_with_object({}) do |vm, h|
+      h[vm.view_name] = vm
+      vm.view_aliases.each do |view_alias|
+        h[view_alias] = vm
+      end
+    end
   end
 end
diff --git a/lib/view_model/active_record/association_manipulation.rb b/lib/view_model/active_record/association_manipulation.rb
index 5d2f01e8..72da73d8 100644
--- a/lib/view_model/active_record/association_manipulation.rb
+++ b/lib/view_model/active_record/association_manipulation.rb
@@ -52,9 +52,7 @@ def load_associated(association_name, scope: nil, eager_include: true, serialize
   def replace_associated(association_name, update_hash, references: {}, deserialize_context: self.class.new_deserialize_context)
     association_data = self.class._association_data(association_name)
 
-    # TODO: structure checking
-
-    if association_data.through? || association_data.shared?
+    if association_data.referenced?
       is_fupdate =
         association_data.collection? &&
         update_hash.is_a?(Hash) &&
@@ -125,10 +123,6 @@ def append_associated(association_name, subtree_hash_or_hashes, references: {},
 
           update_context = ViewModel::ActiveRecord::UpdateContext.build!(root_update_data, referenced_update_data, root_type: direct_viewmodel_class)
 
-          # Provide information about what was updated
-          deserialize_context.updated_associations = root_update_data.map(&:updated_associations)
-                                                       .inject({}) { |acc, assocs| acc.deep_merge(assocs) }
-
           # Set new parent
           new_parent = ViewModel::ActiveRecord::UpdateOperation::ParentData.new(direct_reflection.inverse_of, self)
           update_context.root_updates.each { |update| update.reparent_to = new_parent }
@@ -177,15 +171,26 @@ def append_associated(association_name, subtree_hash_or_hashes, references: {},
           child_context = self.context_for_child(association_name, context: deserialize_context)
           updated_viewmodels = update_context.run!(deserialize_context: child_context)
 
+          # Propagate changes and finalize the parent
+          updated_viewmodels.each do |child|
+            child_changes = child.previous_changes
+
+            if association_data.nested?
+              nested_children_changed!     if child_changes.changed_nested_tree?
+              referenced_children_changed! if child_changes.changed_referenced_children?
+            elsif association_data.owned?
+              referenced_children_changed! if child_changes.changed_owned_tree?
+            end
+          end
+
+          final_changes = self.clear_changes!
+
           if association_data.through?
             updated_viewmodels.map! do |direct_vm|
               direct_vm._read_association(association_data.indirect_reflection.name)
             end
           end
 
-          # Finalize the parent
-          final_changes = self.clear_changes!
-
           # Could happen if hooks attempted to change the parent, which aren't
           # valid since we're only editing children here.
           unless final_changes.contained_to?(associations: [association_name.to_s])
@@ -269,7 +274,12 @@ def delete_associated(association_name, associated_id, type: nil, deserialize_co
           association.delete(child_vm.model)
         end
 
-        self.children_changed!
+        if association_data.nested?
+          nested_children_changed!
+        elsif association_data.owned?
+          referenced_children_changed!
+        end
+
         final_changes = self.clear_changes!
 
         unless final_changes.contained_to?(associations: [association_name.to_s])
@@ -286,7 +296,7 @@ def delete_associated(association_name, associated_id, type: nil, deserialize_co
 
   private
 
-  def construct_direct_append_updates(association_data, subtree_hashes, references)
+  def construct_direct_append_updates(_association_data, subtree_hashes, references)
     ViewModel::ActiveRecord::UpdateData.parse_hashes(subtree_hashes, references)
   end
 
diff --git a/lib/view_model/active_record/cache.rb b/lib/view_model/active_record/cache.rb
index a0abc9f6..bcebc38b 100644
--- a/lib/view_model/active_record/cache.rb
+++ b/lib/view_model/active_record/cache.rb
@@ -198,7 +198,7 @@ def find_and_preload_viewmodels(viewmodel_class, ids, available_viewmodels: nil)
       end
 
       ViewModel.preload_for_serialization(viewmodels,
-                                          include_shared: false,
+                                          include_referenced: false,
                                           lock: "FOR SHARE",
                                           serialize_context: serialize_context)
 
@@ -259,7 +259,7 @@ def cache_name
   end
 
   def cache_version
-    version_string = @viewmodel_class.deep_schema_version(include_shared: false).to_a.sort.join(',')
+    version_string = @viewmodel_class.deep_schema_version(include_referenced: false).to_a.sort.join(',')
     Base64.urlsafe_encode64(Digest::MD5.digest(version_string))
   end
 end
diff --git a/lib/view_model/active_record/cache/cacheable_view.rb b/lib/view_model/active_record/cache/cacheable_view.rb
index 318d9436..9d7c3dae 100644
--- a/lib/view_model/active_record/cache/cacheable_view.rb
+++ b/lib/view_model/active_record/cache/cacheable_view.rb
@@ -39,12 +39,12 @@ def serialize_from_cache(views, serialize_context:)
     end
   end
 
-  # Clear the cache if the view or its owned children were changed during
+  # Clear the cache if the view or its nested children were changed during
   # deserialization
   def after_deserialize(deserialize_context:, changes:)
     super if defined?(super)
 
-    if !changes.new? && changes.changed_tree?
+    if !changes.new? && changes.changed_nested_tree?
       CacheClearer.new(self.class.viewmodel_cache, id).add_to_transaction
     end
   end
diff --git a/lib/view_model/active_record/cloner.rb b/lib/view_model/active_record/cloner.rb
index 78dd6e25..07052b5f 100644
--- a/lib/view_model/active_record/cloner.rb
+++ b/lib/view_model/active_record/cloner.rb
@@ -1,8 +1,10 @@
+# frozen_string_literal: true
+
 # Simple visitor for cloning models through the tree structure defined by
 # ViewModel::ActiveRecord. Owned associations will be followed and cloned, while
-# shared associations will be copied directly. Attributes (including association
-# foreign keys not covered by ViewModel `association`s) will be copied from the
-# original.
+# non-owned referenced associations will be copied directly as references.
+# Attributes (including association foreign keys not covered by ViewModel
+# `association`s) will be copied from the original.
 #
 # To customize, subclasses may define methods `visit_x_view(node, new_model)`
 # for each type they wish to affect. These callbacks may update attributes of
@@ -19,9 +21,9 @@ def clone(node)
     return nil if ignored?
 
     if node.class.name
-      class_name      = node.class.name.underscore.gsub('/', '__')
-      visit     = :"visit_#{class_name}"
-      end_visit = :"end_visit_#{class_name}"
+      class_name = node.class.name.underscore.gsub('/', '__')
+      visit      = :"visit_#{class_name}"
+      end_visit  = :"end_visit_#{class_name}"
     end
 
     if visit && respond_to?(visit, true)
@@ -44,7 +46,7 @@ def clone(node)
 
         if associated.nil?
           new_associated = nil
-        elsif association_data.shared? && !association_data.through?
+        elsif !association_data.owned? && !association_data.through?
           # simply attach the associated target to the new model
           new_associated = associated
         else
@@ -82,11 +84,9 @@ def clone(node)
     new_model
   end
 
-  def pre_visit(node, new_model)
-  end
+  def pre_visit(node, new_model); end
 
-  def post_visit(node, new_model)
-  end
+  def post_visit(node, new_model); end
 
   private
 
diff --git a/lib/view_model/active_record/controller.rb b/lib/view_model/active_record/controller.rb
index fd8a4306..aff1d249 100644
--- a/lib/view_model/active_record/controller.rb
+++ b/lib/view_model/active_record/controller.rb
@@ -46,8 +46,6 @@ def create(serialize_context: new_serialize_context, deserialize_context: new_de
     pre_rendered = viewmodel_class.transaction do
       view = viewmodel_class.deserialize_from_view(update_hash, references: refs, deserialize_context: deserialize_context)
 
-      serialize_context.add_includes(deserialize_context.updated_associations)
-
       view = yield(view) if block_given?
 
       ViewModel.preload_for_serialization(view, serialize_context: serialize_context)
diff --git a/lib/view_model/active_record/update_context.rb b/lib/view_model/active_record/update_context.rb
index 6a9e6b67..35227f8e 100644
--- a/lib/view_model/active_record/update_context.rb
+++ b/lib/view_model/active_record/update_context.rb
@@ -74,7 +74,7 @@ def root_updates
 
     def initialize
       @root_update_operations       = [] # The subject(s) of this update
-      @referenced_update_operations = {} # Shared data updates, referred to by a ref hash
+      @referenced_update_operations = {} # data updates to other root models, referred to by a ref hash
 
       # Set of ViewModel::Reference used to assert only a single update is
       # present for each viewmodel
@@ -178,8 +178,20 @@ def assemble_update_tree
           raise ViewModel::DeserializationError::ParentNotFound.new(@worklist.keys)
         end
 
-        deferred_update = @worklist.delete(key)
-        deferred_update.viewmodel = @release_pool.claim_from_pool(key)
+        deferred_update    = @worklist.delete(key)
+        released_viewmodel = @release_pool.claim_from_pool(key)
+
+        if deferred_update.viewmodel
+          # Deferred reference updates already have a viewmodel: ensure it
+          # matches the tree
+          unless deferred_update.viewmodel == released_viewmodel
+            raise ViewModel::DeserializationError::Internal.new(
+                    "Released viewmodel doesn't match reference update", blame_reference)
+          end
+        else
+          deferred_update.viewmodel = released_viewmodel
+        end
+
         deferred_update.build!(self)
       end
 
@@ -201,6 +213,12 @@ def new_deferred_update(viewmodel_reference, update_data, reparent_to: nil, repo
       update_operation = ViewModel::ActiveRecord::UpdateOperation.new(
         nil, update_data, reparent_to: reparent_to, reposition_to: reposition_to)
       check_unique_update!(viewmodel_reference)
+      defer_update(viewmodel_reference, update_operation)
+    end
+
+    # Defer an existing update: used if we need to ensure that an owned
+    # reference has been freed before we use it.
+    def defer_update(viewmodel_reference, update_operation)
       @worklist[viewmodel_reference] = update_operation
     end
 
diff --git a/lib/view_model/active_record/update_data.rb b/lib/view_model/active_record/update_data.rb
index 02d2d31e..7346cc3e 100644
--- a/lib/view_model/active_record/update_data.rb
+++ b/lib/view_model/active_record/update_data.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'renum'
 require 'view_model/schemas'
 
@@ -45,14 +47,13 @@ def initialize(removed_vm_refs)
     end
   end
 
-  # Parser for collection updates. Collection updates have a regular
-  # structure, but vary based on the contents. Parsing a {direct,
-  # owned} collection recurses deeply and creates a tree of
-  # UpdateDatas, while parsing a {through, shared} collection collects
-  # reference strings.
+  # Parser for collection updates. Collection updates have a regular structure,
+  # but vary based on the contents. Parsing a nested collection recurses deeply
+  # and creates a tree of UpdateDatas, while parsing a referenced collection
+  # collects reference strings.
   class AbstractCollectionUpdate
-    # Wraps a complete collection of new data: either UpdateDatas for owned
-    # collections or reference strings for shared.
+    # Wraps a complete collection of new data: either UpdateDatas for non-root
+    # associations or reference strings for root.
     class Replace
       attr_reader :contents
       def initialize(contents)
@@ -61,7 +62,8 @@ def initialize(contents)
     end
 
     # Wraps an ordered list of FunctionalUpdates, each of whose `contents` are
-    # either UpdateData for owned collections or references for shared.
+    # either UpdateData for nested associations or references for referenced
+    # associations.
     class Functional
       attr_reader :actions
       def initialize(actions)
@@ -81,8 +83,8 @@ def vm_references(update_context)
 
       # Resolve ViewModel::References used in the update's contents, whether by
       # reference or value.
-      def used_vm_refs(update_context)
-        raise "abstract"
+      def used_vm_refs(_update_context)
+        raise RuntimeError.new('abstract method')
       end
 
       def removed_vm_refs
@@ -153,7 +155,8 @@ def parse_action(action)
       # The shape of the actions are always the same
 
       # Parse an anchor for a functional_update, before/after
-      # May only contain type and id fields, is never a reference even for shared collections.
+      # May only contain type and id fields, is never a reference even for
+      # referenced associations.
       def parse_anchor(child_hash) # final
         child_metadata = ViewModel.extract_reference_only_metadata(child_hash)
 
@@ -271,9 +274,13 @@ class Functional < AbstractCollectionUpdate::Functional
 
       def used_vm_refs(update_context)
         update_datas
-          .map { |upd| upd.viewmodel_reference if upd.id }
+          .map { |upd| resolve_vm_reference(upd, update_context) }
           .compact
       end
+
+      def resolve_vm_reference(update_data, _update_context)
+        update_data.viewmodel_reference if update_data.id
+      end
     end
 
     class Parser < AbstractCollectionUpdate::Parser
@@ -319,9 +326,13 @@ class Functional < AbstractCollectionUpdate::Functional
 
       def used_vm_refs(update_context)
         references.map do |ref|
-          update_context.resolve_reference(ref, nil).viewmodel_reference
+          resolve_vm_reference(ref, update_context)
         end
       end
+
+      def resolve_vm_reference(ref, update_context)
+        update_context.resolve_reference(ref, nil).viewmodel_reference
+      end
     end
 
     class Parser < AbstractCollectionUpdate::Parser
@@ -356,6 +367,7 @@ def parse_contents(values)
           unless valid_reference_keys.include?(ref)
             raise ViewModel::DeserializationError::InvalidSharedReference.new(ref, blame_reference)
           end
+
           ref
         end
       end
@@ -421,7 +433,7 @@ module Schemas
       fupdate_owned =
         fupdate_base.(ViewModel::Schemas::VIEWMODEL_UPDATE_SCHEMA)
 
-      fupdate_shared           =
+      fupdate_shared =
         fupdate_base.({ 'oneOf' => [ViewModel::Schemas::VIEWMODEL_REFERENCE_SCHEMA,
                                     viewmodel_reference_only] })
 
@@ -571,30 +583,15 @@ def to_sequence(name, value)
       case
       when value.nil?
         []
-      when association_data.shared?
+      when association_data.referenced?
         []
-      when association_data.collection? # not shared, because of shared? check above
+      when association_data.collection? # nested, because of referenced? check above
         value.update_datas
       else
         [value]
       end
     end
 
-    # Updates in terms of viewmodel associations
-    def updated_associations
-      deps = {}
-
-      (associations.merge(referenced_associations)).each do |assoc_name, assoc_update|
-        deps[assoc_name] =
-          to_sequence(assoc_name, assoc_update)
-            .each_with_object({}) do |update_data, updated_associations|
-              updated_associations.deep_merge!(update_data.updated_associations)
-            end
-      end
-
-      deps
-    end
-
     def build_preload_specs(association_data, updates)
       if association_data.polymorphic?
         updates.map do |update_data|
@@ -682,6 +679,7 @@ def parse(hash_data, valid_reference_keys)
 
         when AssociationData
           association_data = member_data
+
           case
           when value.nil?
             if association_data.collection?
@@ -689,28 +687,28 @@ def parse(hash_data, valid_reference_keys)
                       "Invalid collection update value 'nil' for association '#{name}'",
                       blame_reference)
             end
-            if association_data.shared?
+            if association_data.referenced?
               referenced_associations[name] = nil
             else
               associations[name] = nil
             end
 
-          when association_data.through?
-            referenced_associations[name] =
-              ReferencedCollectionUpdate::Parser
-                .new(association_data, blame_reference, valid_reference_keys)
-                .parse(value)
+          when association_data.referenced?
+            if association_data.collection?
+              referenced_associations[name] =
+                ReferencedCollectionUpdate::Parser
+                  .new(association_data, blame_reference, valid_reference_keys)
+                  .parse(value)
+            else
+              # Extract and check reference
+              ref = ViewModel.extract_reference_metadata(value)
 
-          when association_data.shared?
-            # Extract and check reference
-            ref = ViewModel.extract_reference_metadata(value)
+              unless valid_reference_keys.include?(ref)
+                raise ViewModel::DeserializationError::InvalidSharedReference.new(ref, blame_reference)
+              end
 
-            unless valid_reference_keys.include?(ref)
-              raise ViewModel::DeserializationError::InvalidSharedReference.new(ref, blame_reference)
+              referenced_associations[name] = ref
             end
-
-            referenced_associations[name] = ref
-
           else
             if association_data.collection?
               associations[name] =
diff --git a/lib/view_model/active_record/update_operation.rb b/lib/view_model/active_record/update_operation.rb
index 9b1e2c45..ada95837 100644
--- a/lib/view_model/active_record/update_operation.rb
+++ b/lib/view_model/active_record/update_operation.rb
@@ -40,10 +40,6 @@ def viewmodel_reference
       end
     end
 
-    def deferred?
-      viewmodel.nil?
-    end
-
     def built?
       @built
     end
@@ -112,9 +108,8 @@ def run!(deserialize_context:)
               if child_operation
                 child_ctx = viewmodel.context_for_child(association_data.association_name, context: deserialize_context)
                 child_viewmodel = child_operation.run!(deserialize_context: child_ctx)
-                if !association_data.shared? && child_viewmodel.previous_changes.changed_tree?
-                  viewmodel.children_changed!
-                end
+                propagate_tree_changes(association_data, child_viewmodel.previous_changes)
+
                 child_viewmodel.model
               end
             association.writer(new_target)
@@ -153,9 +148,8 @@ def run!(deserialize_context:)
               if child_operation
                 ViewModel::Utils.map_one_or_many(child_operation) do |op|
                   child_viewmodel = op.run!(deserialize_context: child_ctx)
-                  if !association_data.shared? && child_viewmodel.previous_changes.changed_tree?
-                    viewmodel.children_changed!
-                  end
+                  propagate_tree_changes(association_data, child_viewmodel.previous_changes)
+
                   child_viewmodel.model
                 end
               end
@@ -183,7 +177,11 @@ def run!(deserialize_context:)
                 child_hook_control.record_changes(changes)
               end
 
-              viewmodel.children_changed! unless child_association_data.shared?
+              if child_association_data.nested?
+                viewmodel.nested_children_changed!
+              elsif child_association_data.owned?
+                viewmodel.referenced_children_changed!
+              end
             end
             debug "<- #{debug_name}: Finished checking released children permissions"
           end
@@ -208,9 +206,18 @@ def run!(deserialize_context:)
       raise ViewModel::DeserializationError::DatabaseConstraint.from_exception(ex, blame_reference)
     end
 
+    def propagate_tree_changes(association_data, child_changes)
+      if association_data.nested?
+        viewmodel.nested_children_changed!     if child_changes.changed_nested_tree?
+        viewmodel.referenced_children_changed! if child_changes.changed_referenced_children?
+      elsif association_data.owned?
+        viewmodel.referenced_children_changed! if child_changes.changed_owned_tree?
+      end
+    end
+
     # Recursively builds UpdateOperations for the associations in our UpdateData
     def build!(update_context)
-      raise ViewModel::DeserializationError::Internal.new("Internal error: UpdateOperation cannot build a deferred update") if deferred?
+      raise ViewModel::DeserializationError::Internal.new("Internal error: UpdateOperation cannot build a deferred update") if viewmodel.nil?
       return self if built?
 
       update_data.associations.each do |association_name, association_update_data|
@@ -231,8 +238,10 @@ def build!(update_context)
         update =
           if association_data.through?
             build_updates_for_collection_referenced_association(association_data, reference_string, update_context)
+          elsif association_data.collection?
+            build_updates_for_collection_association(association_data, reference_string, update_context)
           else
-            build_update_for_single_referenced_association(association_data, reference_string, update_context)
+            build_update_for_single_association(association_data, reference_string, update_context)
           end
 
         add_update(association_data, update)
@@ -254,38 +263,6 @@ def add_update(association_data, update)
 
     private
 
-    def build_update_for_single_referenced_association(association_data, reference_string, update_context)
-      # TODO intern loads for shared items so we only load them once
-      model = self.viewmodel.model
-      previous_child_viewmodel = model.public_send(association_data.direct_reflection.name).try do |previous_child_model|
-        vm_class = association_data.viewmodel_class_for_model!(previous_child_model.class)
-        vm_class.new(previous_child_model)
-      end
-
-      if reference_string.nil?
-        referred_update    = nil
-        referred_viewmodel = nil
-      else
-        referred_update    = update_context.resolve_reference(reference_string, blame_reference)
-        referred_viewmodel = referred_update.viewmodel
-
-        unless association_data.accepts?(referred_viewmodel.class)
-          raise ViewModel::DeserializationError::InvalidAssociationType.new(
-            association_data.association_name.to_s,
-            referred_viewmodel.class.view_name,
-            blame_reference)
-        end
-
-        referred_update.build!(update_context)
-      end
-
-      if previous_child_viewmodel != referred_viewmodel
-        viewmodel.association_changed!(association_data.association_name)
-      end
-
-      referred_update
-    end
-
     # Resolve or construct viewmodels for incoming update data. Where a child
     # hash references an existing model not currently attached to this parent,
     # it must be found before recursing into that child. If the model is
@@ -321,6 +298,60 @@ def resolve_child_viewmodels(association_data, update_datas, previous_child_view
       end
     end
 
+    def resolve_referenced_viewmodels(association_data, update_datas, previous_child_viewmodels, update_context)
+      previous_child_viewmodels = Array.wrap(previous_child_viewmodels).index_by(&:to_reference)
+
+      ViewModel::Utils.map_one_or_many(update_datas) do |update_data|
+        if update_data.is_a?(UpdateData)
+          # Dummy child update data for an unmodified previous child of a
+          # functional update; create it an empty update operation.
+          viewmodel = previous_child_viewmodels.fetch(update_data.viewmodel_reference)
+          update    = update_context.new_update(viewmodel, update_data)
+          next [update, viewmodel]
+        end
+
+        reference_string = update_data
+        child_update     = update_context.resolve_reference(reference_string, blame_reference)
+        child_viewmodel  = child_update.viewmodel
+
+        unless association_data.accepts?(child_viewmodel.class)
+          raise ViewModel::DeserializationError::InvalidAssociationType.new(
+                  association_data.association_name.to_s,
+                  child_viewmodel.class.view_name,
+                  blame_reference)
+        end
+
+        child_ref = child_viewmodel.to_reference
+
+        # The case of two potential owners trying to claim a new referenced
+        # child is covered by set_reference_update_parent.
+        claimed = !association_data.owned? ||
+                  child_update.update_data.new? ||
+                  previous_child_viewmodels.has_key?(child_ref) ||
+                  update_context.try_take_released_viewmodel(child_ref).present?
+
+        if claimed
+          [child_update, child_viewmodel]
+        else
+          # Return the reference to indicate a deferred update
+          [child_update, child_ref]
+        end
+      end
+    end
+
+    def set_reference_update_parent(association_data, update, parent_data)
+      if update.reparent_to
+        # Another parent has already tried to take this (probably new)
+        # owned referenced view. It can only be claimed by one of them.
+        other_parent = update.reparent_to.viewmodel.to_reference
+        raise ViewModel::DeserializationError::DuplicateOwner.new(
+                association_data.association_name,
+                [blame_reference, other_parent])
+      end
+
+      update.reparent_to = parent_data
+    end
+
     def build_update_for_single_association(association_data, association_update_data, update_context)
       model = self.viewmodel.model
 
@@ -329,25 +360,63 @@ def build_update_for_single_association(association_data, association_update_dat
         vm_class.new(previous_child_model)
       end
 
-      if previous_child_viewmodel.present?
-        # Clear the cached association so that AR's save behaviour doesn't
-        # conflict with our explicit parent updates.  If we still have a child
-        # after the update, we'll either call `Association#writer` or manually
-        # fix the target cache after recursing in run!(). If we don't, we promise
-        # that the child will no longer be attached in the database, so the new
-        # cached data of nil will be correct.
-        clear_association_cache(model, association_data.direct_reflection)
+      if association_data.pointer_location == :remote
+        if previous_child_viewmodel.present?
+          # Clear the cached association so that AR's save behaviour doesn't
+          # conflict with our explicit parent updates.  If we still have a child
+          # after the update, we'll either call `Association#writer` or manually
+          # fix the target cache after recursing in run!(). If we don't, we promise
+          # that the child will no longer be attached in the database, so the new
+          # cached data of nil will be correct.
+          clear_association_cache(model, association_data.direct_reflection)
+        end
+
+        reparent_data =
+          ParentData.new(association_data.direct_reflection.inverse_of, viewmodel)
       end
 
-      child_viewmodel =
-        if association_update_data.present?
-          resolve_child_viewmodels(association_data, association_update_data, previous_child_viewmodel, update_context)
+      if association_update_data.present?
+        if association_data.referenced?
+          # resolve reference string
+          reference_string = association_update_data
+          child_update, child_viewmodel = resolve_referenced_viewmodels(association_data, reference_string,
+                                                                        previous_child_viewmodel, update_context)
+
+          if reparent_data
+            set_reference_update_parent(association_data, child_update, reparent_data)
+          end
+
+          if child_viewmodel.is_a?(ViewModel::Reference)
+            update_context.defer_update(child_viewmodel, child_update)
+          end
+        else
+          # Resolve direct children
+          child_viewmodel =
+            resolve_child_viewmodels(association_data, association_update_data, previous_child_viewmodel, update_context)
+
+          child_update =
+            if child_viewmodel.is_a?(ViewModel::Reference)
+              update_context.new_deferred_update(child_viewmodel, association_update_data, reparent_to: reparent_data)
+            else
+              update_context.new_update(child_viewmodel, association_update_data, reparent_to: reparent_data)
+            end
         end
 
+        # Build the update if we've claimed it
+        unless child_viewmodel.is_a?(ViewModel::Reference)
+          child_update.build!(update_context)
+        end
+      else
+        child_update = nil
+        child_viewmodel = nil
+      end
+
+      # Handle changes
       if previous_child_viewmodel != child_viewmodel
         viewmodel.association_changed!(association_data.association_name)
-        # free previous child if present
-        if previous_child_viewmodel.present?
+
+        # free previous child if present and owned
+        if previous_child_viewmodel.present? && association_data.owned?
           if association_data.pointer_location == :local
             # When we free a child that's pointed to from its old parent, we need to
             # clear the cached association to that old parent. If we don't do this,
@@ -358,12 +427,7 @@ def build_update_for_single_association(association_data, association_update_dat
             # model.association(...).inverse_reflection_for(previous_child_model), but
             # that's private.
 
-            inverse_reflection =
-              if association_data.direct_reflection.polymorphic?
-                association_data.direct_reflection.polymorphic_inverse_of(previous_child_viewmodel.model.class)
-              else
-                association_data.direct_reflection.inverse_of
-              end
+            inverse_reflection = association_data.direct_reflection_inverse(previous_child_viewmodel.model.class)
 
             if inverse_reflection.present?
               clear_association_cache(previous_child_viewmodel.model, inverse_reflection)
@@ -374,25 +438,7 @@ def build_update_for_single_association(association_data, association_update_dat
         end
       end
 
-      # Construct and return update for new child viewmodel
-      if child_viewmodel.present?
-        # If the association's pointer is in the child, need to provide it with a
-        # ParentData to update
-        parent_data =
-          if association_data.pointer_location == :remote
-            ParentData.new(association_data.direct_reflection.inverse_of, viewmodel)
-          else
-            nil
-          end
-
-        case child_viewmodel
-        when ViewModel::Reference # deferred
-          vm_ref = child_viewmodel
-          update_context.new_deferred_update(vm_ref, association_update_data, reparent_to: parent_data)
-        else
-          update_context.new_update(child_viewmodel, association_update_data, reparent_to: parent_data).build!(update_context)
-        end
-      end
+      child_update
     end
 
     def build_updates_for_collection_association(association_data, association_update, update_context)
@@ -402,11 +448,13 @@ def build_updates_for_collection_association(association_data, association_updat
       parent_data = ParentData.new(association_data.direct_reflection.inverse_of, viewmodel)
 
       # load children already attached to this model
-      child_viewmodel_class     = association_data.viewmodel_class
+      child_viewmodel_class = association_data.viewmodel_class
+
       previous_child_viewmodels =
         model.public_send(association_data.direct_reflection.name).map do |child_model|
           child_viewmodel_class.new(child_model)
         end
+
       if child_viewmodel_class._list_member?
         previous_child_viewmodels.sort_by!(&:_list_attribute)
       end
@@ -421,114 +469,178 @@ def build_updates_for_collection_association(association_data, association_updat
         clear_association_cache(model, association_data.direct_reflection)
       end
 
-      child_datas =
-        case association_update
-        when OwnedCollectionUpdate::Replace
-          association_update.update_datas
+      # Update contents are either UpdateData in the case of a nested
+      # association, or reference strings in the case of a reference association.
+      # The former are resolved with resolve_child_viewmodels, the latter with
+      # resolve_referenced_viewmodels.
+      resolve_child_data_reference = ->(child_data) do
+        case child_data
+        when UpdateData
+          child_data.viewmodel_reference if child_data.id
+        when String
+          update_context.resolve_reference(child_data, nil).viewmodel_reference
+        else
+          raise ViewModel::DeserializationError::Internal.new(
+                  "Unexpected child data type in collection update: #{child_data.class.name}")
+        end
+      end
 
-        when OwnedCollectionUpdate::Functional
-          child_datas =
-            previous_child_viewmodels.map do |previous_child_viewmodel|
-              UpdateData.empty_update_for(previous_child_viewmodel)
-            end
+      case association_update
+      when AbstractCollectionUpdate::Replace
+        child_datas = association_update.contents
 
-          association_update.check_for_duplicates!(update_context, self.viewmodel.blame_reference)
+      when AbstractCollectionUpdate::Functional
+        # A fupdate isn't permitted to edit the same model twice.
+        association_update.check_for_duplicates!(update_context, blame_reference)
 
-          association_update.actions.each do |fupdate|
-            case fupdate
-            when FunctionalUpdate::Append
-              if fupdate.before || fupdate.after
-                moved_refs  = fupdate.contents.map(&:viewmodel_reference).to_set
-                child_datas = child_datas.reject { |child| moved_refs.include?(child.viewmodel_reference) }
+        # Construct empty updates for previous children
+        child_datas =
+          previous_child_viewmodels.map do |previous_child_viewmodel|
+            UpdateData.empty_update_for(previous_child_viewmodel)
+          end
 
-                ref         = fupdate.before || fupdate.after
-                index       = child_datas.find_index { |cd| cd.viewmodel_reference == ref }
-                unless index
-                  raise ViewModel::DeserializationError::AssociatedNotFound.new(
-                    association_data.association_name.to_s, ref, blame_reference)
-                end
+        # Insert or replace with either real UpdateData or reference strings
+        association_update.actions.each do |fupdate|
+          case fupdate
+          when FunctionalUpdate::Append
+            # If we're referring to existing members, ensure that they're removed before we append/insert
+            existing_refs = fupdate.contents
+                              .map(&resolve_child_data_reference)
+                              .to_set
+
+            child_datas.reject! do |child_data|
+              child_ref = resolve_child_data_reference.(child_data)
+              child_ref && existing_refs.include?(child_ref)
+            end
 
-                index += 1 if fupdate.after
-                child_datas.insert(index, *fupdate.contents)
+            if fupdate.before || fupdate.after
+              rel_ref = fupdate.before || fupdate.after
 
-              else
-                child_datas.concat(fupdate.contents)
+              # Find the relative insert location. This might be an empty
+              # UpdateData from a previous child or an already-fupdated
+              # reference string.
+              index = child_datas.find_index do |child_data|
+                rel_ref == resolve_child_data_reference.(child_data)
+              end
 
+              unless index
+                raise ViewModel::DeserializationError::AssociatedNotFound.new(
+                        association_data.association_name.to_s, rel_ref, blame_reference)
               end
 
-            when FunctionalUpdate::Remove
-              removed_refs = fupdate.removed_vm_refs.to_set
-              child_datas.reject! { |child_data| removed_refs.include?(child_data.viewmodel_reference) }
+              index += 1 if fupdate.after
+              child_datas.insert(index, *fupdate.contents)
+
+            else
+              child_datas.concat(fupdate.contents)
+            end
 
-            when FunctionalUpdate::Update
-              # Already guaranteed that each ref has a single data attached
-              new_datas = fupdate.contents.index_by(&:viewmodel_reference)
+          when FunctionalUpdate::Remove
+            removed_refs = fupdate.removed_vm_refs.to_set
+            child_datas.reject! do |child_data|
+              child_ref = resolve_child_data_reference.(child_data)
+              removed_refs.include?(child_ref)
+            end
 
-              child_datas = child_datas.map do |child_data|
-                ref = child_data.viewmodel_reference
-                new_datas.delete(ref) { child_data }
-              end
+          when FunctionalUpdate::Update
+            # Already guaranteed that each ref has a single existing child attached
+            new_child_datas = fupdate.contents.index_by(&resolve_child_data_reference)
 
-              # Assertion that all values in update_op.values are present in the collection
-              unless new_datas.empty?
-                raise ViewModel::DeserializationError::AssociatedNotFound.new(
-                  association_data.association_name.to_s, new_datas.keys, blame_reference)
-              end
-            else
-              raise ViewModel::DeserializationError::InvalidSyntax.new(
-                "Unknown functional update type: '#{fupdate.type}'",
-                blame_reference)
+            # Replace matched child_datas with the update contents.
+            child_datas.map! do |child_data|
+              child_ref = resolve_child_data_reference.(child_data)
+              new_child_datas.delete(child_ref) { child_data }
             end
+
+            # Assertion that all values in the update were found in child_datas
+            unless new_child_datas.empty?
+              raise ViewModel::DeserializationError::AssociatedNotFound.new(
+                      association_data.association_name.to_s, new_child_datas.keys, blame_reference)
+            end
+          else
+            raise ViewModel::DeserializationError::InvalidSyntax.new(
+                    "Unknown functional update type: '#{fupdate.type}'",
+                    blame_reference)
           end
+        end
+      end
+
+      if association_data.referenced?
+        # child_datas are either pre-resolved UpdateData (for non-fupdated
+        # existing members) or reference strings. Resolve into pairs of
+        # [UpdateOperation, ViewModel] if we can create or claim the
+        # UpdateOperation or [UpdateOperation, ViewModelReference] otherwise.
+        resolved_children =
+          resolve_referenced_viewmodels(association_data, child_datas, previous_child_viewmodels, update_context)
 
-          child_datas
+        resolved_children.each do |child_update, child_viewmodel|
+          set_reference_update_parent(association_data, child_update, parent_data)
+
+          if child_viewmodel.is_a?(ViewModel::Reference)
+            update_context.defer_update(child_viewmodel, child_update)
+          end
         end
 
-      child_viewmodels = resolve_child_viewmodels(association_data, child_datas, previous_child_viewmodels, update_context)
+      else
+        # child datas are all UpdateData
+        child_viewmodels = resolve_child_viewmodels(association_data, child_datas, previous_child_viewmodels, update_context)
 
-      # if the new children differ, including in order, mark that one of our
-      # associations has changed and release any no-longer-attached children
-      if child_viewmodels != previous_child_viewmodels
-        viewmodel.association_changed!(association_data.association_name)
-        released_child_viewmodels = previous_child_viewmodels - child_viewmodels
-        released_child_viewmodels.each do |vm|
-          release_viewmodel(vm, association_data, update_context)
+        resolved_children = child_datas.zip(child_viewmodels).map do |child_data, child_viewmodel|
+          child_update =
+            if child_viewmodel.is_a?(ViewModel::Reference)
+              update_context.new_deferred_update(child_viewmodel, child_data, reparent_to: parent_data)
+            else
+              update_context.new_update(child_viewmodel, child_data, reparent_to: parent_data)
+            end
+
+          [child_update, child_viewmodel]
         end
       end
 
       # Calculate new positions for children if in a list. Ignore previous
-      # positions for unresolved references: they'll always need to be updated
-      # anyway since their parent pointer will change.
-      new_positions = Array.new(child_viewmodels.length)
+      # positions (i.e. return nil) for unresolved references: they'll always
+      # need to be updated anyway since their parent pointer will change.
+      new_positions = Array.new(resolved_children.length)
 
       if association_data.viewmodel_class._list_member?
         set_position = ->(index, pos) { new_positions[index] = pos }
+
         get_previous_position = ->(index) do
-          vm = child_viewmodels[index]
+          vm = resolved_children[index][1]
           vm._list_attribute unless vm.is_a?(ViewModel::Reference)
         end
 
         ActsAsManualList.update_positions(
-          (0...child_viewmodels.size).to_a, # indexes
+          (0...resolved_children.size).to_a, # indexes
           position_getter: get_previous_position,
           position_setter: set_position)
       end
 
-      # Recursively build update operations for children
-      child_updates = child_viewmodels.zip(child_datas, new_positions).map do |child_viewmodel, association_update_data, position|
-        case child_viewmodel
-        when ViewModel::Reference # deferred
-          reference = child_viewmodel
-          update_context.new_deferred_update(reference, association_update_data, reparent_to: parent_data, reposition_to: position)
-        else
-          update_context.new_update(child_viewmodel, association_update_data, reparent_to: parent_data, reposition_to: position).build!(update_context)
+      resolved_children.zip(new_positions).each do |(child_update, child_viewmodel), new_position|
+        child_update.reposition_to = new_position
+
+        # Recurse into building child updates that we've claimed
+        unless child_viewmodel.is_a?(ViewModel::Reference)
+          child_update.build!(update_context)
+        end
+      end
+
+      child_updates, child_viewmodels = resolved_children.transpose.presence || [[], []]
+
+      # if the new children differ, including in order, mark that this
+      # association has changed and release any no-longer-attached children
+      if child_viewmodels != previous_child_viewmodels
+        viewmodel.association_changed!(association_data.association_name)
+
+        released_child_viewmodels = previous_child_viewmodels - child_viewmodels
+        released_child_viewmodels.each do |vm|
+          release_viewmodel(vm, association_data, update_context)
         end
       end
 
       child_updates
     end
 
-
     class ReferencedCollectionMember
       attr_reader   :indirect_viewmodel_reference, :direct_viewmodel
       attr_accessor :ref_string, :position
@@ -694,7 +806,7 @@ def build_updates_for_collection_referenced_association(association_data, associ
       target_collection = MutableReferencedCollection.new(
         association_data, update_context, previous_members, blame_reference)
 
-      # All updates to shared collections produce a complete target list of
+      # All updates to referenced collections produce a complete target list of
       # ReferencedCollectionMembers including a ViewModel::Reference to the
       # indirect child, and an existing (from previous) or new ViewModel for the
       # direct child.
diff --git a/lib/view_model/active_record/visitor.rb b/lib/view_model/active_record/visitor.rb
index 6d74e692..d22d22d9 100644
--- a/lib/view_model/active_record/visitor.rb
+++ b/lib/view_model/active_record/visitor.rb
@@ -1,11 +1,12 @@
 # frozen_string_literal: true
 
 class ViewModel::ActiveRecord::Visitor
-  attr_reader :visit_shared, :for_edit
+  attr_reader :visit_referenced, :visit_shared, :for_edit
 
-  def initialize(visit_shared: true, for_edit: false)
-    @visit_shared = visit_shared
-    @for_edit     = for_edit
+  def initialize(visit_referenced: true, visit_shared: true, for_edit: false)
+    @visit_referenced = visit_referenced
+    @visit_shared     = visit_shared
+    @for_edit         = for_edit
   end
 
   def visit(view, context: nil)
@@ -29,8 +30,10 @@ def visit(view, context: nil)
       # visit the underlying viewmodel for each association, ignoring any
       # customization
       view.class._members.each do |name, member_data|
-        next unless member_data.is_a?(ViewModel::ActiveRecord::AssociationData)
-        next if member_data.shared? && !visit_shared
+        next unless member_data.association?
+        next if member_data.referenced? && !visit_referenced
+        next if !member_data.owned? && !visit_shared
+
         children = Array.wrap(view._read_association(name))
         children.each do |child|
           if context
diff --git a/lib/view_model/changes.rb b/lib/view_model/changes.rb
index 00153f9a..3b662fa7 100644
--- a/lib/view_model/changes.rb
+++ b/lib/view_model/changes.rb
@@ -5,18 +5,20 @@
 class ViewModel::Changes
   using ViewModel::Utils::Collections
 
-  attr_reader :new, :changed_attributes, :changed_associations, :changed_children, :deleted
+  attr_reader :new, :changed_attributes, :changed_associations, :changed_nested_children, :changed_referenced_children, :deleted
 
   alias new? new
   alias deleted? deleted
-  alias changed_children? changed_children
+  alias changed_nested_children? changed_nested_children
+  alias changed_referenced_children? changed_referenced_children
 
-  def initialize(new: false, changed_attributes: [], changed_associations: [], changed_children: false, deleted: false)
-    @new                  = new
-    @changed_attributes   = changed_attributes.map(&:to_s)
-    @changed_associations = changed_associations.map(&:to_s)
-    @changed_children     = changed_children
-    @deleted              = deleted
+  def initialize(new: false, changed_attributes: [], changed_associations: [], changed_nested_children: false, changed_referenced_children: false, deleted: false)
+    @new                         = new
+    @changed_attributes          = changed_attributes.map(&:to_s)
+    @changed_associations        = changed_associations.map(&:to_s)
+    @changed_nested_children     = changed_nested_children
+    @changed_referenced_children = changed_referenced_children
+    @deleted                     = deleted
   end
 
   def contained_to?(associations: [], attributes: [])
@@ -34,17 +36,22 @@ def changed?
     new? || deleted? || changed_attributes.present? || changed_associations.present?
   end
 
-  def changed_tree?
-    changed? || changed_children?
+  def changed_nested_tree?
+    changed? || changed_nested_children?
+  end
+
+  def changed_owned_tree?
+    changed? || changed_nested_children? || changed_referenced_children?
   end
 
   def to_h
     {
-      'changed_attributes'   => changed_attributes.dup,
-      'changed_associations' => changed_associations.dup,
-      'new'                  => new?,
-      'changed_children'     => changed_children?,
-      'deleted'              => deleted?,
+      'changed_attributes'          => changed_attributes.dup,
+      'changed_associations'        => changed_associations.dup,
+      'new'                         => new?,
+      'changed_nested_children'     => changed_nested_children?,
+      'changed_referenced_children' => changed_referenced_children?,
+      'deleted'                     => deleted?,
     }
   end
 
@@ -52,7 +59,8 @@ def ==(other)
     return false unless other.is_a?(ViewModel::Changes)
 
     self.new? == other.new? &&
-      self.changed_children? == other.changed_children? &&
+      self.changed_nested_children? == other.changed_nested_children? &&
+      self.changed_referenced_children? == other.changed_referenced_children? &&
       self.deleted? == other.deleted? &&
       self.changed_attributes.contains_exactly?(other.changed_attributes) &&
       self.changed_associations.contains_exactly?(other.changed_associations)
diff --git a/lib/view_model/config.rb b/lib/view_model/config.rb
index ca9baa25..a6c2bc1b 100644
--- a/lib/view_model/config.rb
+++ b/lib/view_model/config.rb
@@ -10,7 +10,7 @@
 
 class ViewModel::Config
   def self.configure!(&block)
-    if instance_variable_defined?(:@instance)
+    if configured?
       raise ArgumentError.new('ViewModel library already configured')
     end
 
@@ -18,8 +18,12 @@ def self.configure!(&block)
     @instance = builder.build!(&block)
   end
 
+  def self.configured?
+    instance_variable_defined?(:@instance)
+  end
+
   def self._option(opt)
-    configure! unless instance_variable_defined?(:@instance)
+    configure! unless configured?
     @instance[opt]
   end
 
diff --git a/lib/view_model/deserialization_error.rb b/lib/view_model/deserialization_error.rb
index 3e06f7ff..6c776261 100644
--- a/lib/view_model/deserialization_error.rb
+++ b/lib/view_model/deserialization_error.rb
@@ -226,6 +226,19 @@ def meta
       end
     end
 
+    class DuplicateOwner < InvalidRequest
+      attr_reader :association_name
+
+      def initialize(association_name, parents)
+        @association_name = association_name
+        super(parents)
+      end
+
+      def detail
+        "Multiple parents attempted to claim the same owned '#{association_name}' reference: " + nodes.map(&:to_s).join(", ")
+      end
+    end
+
     class ParentNotFound < NotFound
       def detail
         "Could not resolve release from previous parent for the following owned viewmodel(s): " +
@@ -251,6 +264,24 @@ def meta
       end
     end
 
+    class ReadOnlyAssociation < DeserializationError
+      status 400
+      attr_reader :association
+
+      def initialize(association, node)
+        @association = association
+        super([node])
+      end
+
+      def detail
+        "Cannot edit read only association '#{association}'"
+      end
+
+      def meta
+        super.merge(association: association)
+      end
+    end
+
     class ReadOnlyType < DeserializationError
       status 400
       detail "Deserialization not defined for view type"
diff --git a/lib/view_model/deserialize_context.rb b/lib/view_model/deserialize_context.rb
index f91041be..1b99112f 100644
--- a/lib/view_model/deserialize_context.rb
+++ b/lib/view_model/deserialize_context.rb
@@ -1,16 +1,12 @@
+# frozen_string_literal: true
+
 require 'view_model/traversal_context'
 
 class ViewModel::DeserializeContext < ViewModel::TraversalContext
   class SharedContext < ViewModel::TraversalContext::SharedContext
-    # During deserialization, collects a tree of viewmodel association names that
-    # were updated. Used to ensure that updated associations are always included
-    # in response serialization after deserialization, even if hidden by default.
-    attr_accessor :updated_associations
   end
 
   def self.shared_context_class
     SharedContext
   end
-
-  delegate :updated_associations, :"updated_associations=", to: :shared_context
 end
diff --git a/lib/view_model/record.rb b/lib/view_model/record.rb
index 9c62d1f6..ef84437a 100644
--- a/lib/view_model/record.rb
+++ b/lib/view_model/record.rb
@@ -36,22 +36,30 @@ def should_register?
     end
 
     # Specifies an attribute from the model to be serialized in this view
-    def attribute(attr, as: nil, read_only: false, write_once: false, using: nil, format: nil, array: false, optional: false)
+    def attribute(attr, as: nil, read_only: false, write_once: false, using: nil, format: nil, array: false)
       model_attribute_name = attr.to_s
       vm_attribute_name    = (as || attr).to_s
 
       if using && format
-        raise ArgumentError.new("Only one of :using and :format may be specified")
+        raise ArgumentError.new("Only one of ':using' and ':format' may be specified")
       end
       if using && !(using.is_a?(Class) && using < ViewModel)
         raise ArgumentError.new("Invalid 'using:' viewmodel: not a viewmodel class")
       end
+      if using && using.root?
+        raise ArgumentError.new("Invalid 'using:' viewmodel: is a root")
+      end
       if format && !format.respond_to?(:dump) && !format.respond_to?(:load)
         raise ArgumentError.new("Invalid 'format:' serializer: must respond to :dump and :load")
       end
 
-      attr_data = AttributeData.new(vm_attribute_name, model_attribute_name, using, format,
-                                    array, optional, read_only, write_once)
+      attr_data = AttributeData.new(name: vm_attribute_name,
+                                    model_attr_name: model_attribute_name,
+                                    attribute_viewmodel: using,
+                                    attribute_serializer: format,
+                                    array: array,
+                                    read_only: read_only,
+                                    write_once: write_once)
       _members[vm_attribute_name] = attr_data
 
       @generated_accessor_module.module_eval do
@@ -166,9 +174,10 @@ def initialize(model)
 
     self.model = model
 
-    @new_model          = false
-    @changed_attributes = []
-    @changed_children   = false
+    @new_model                     = false
+    @changed_attributes            = []
+    @changed_nested_children       = false
+    @changed_referenced_children   = false
   end
 
   # VM::Record identity matches the identity of its model. If the model has a
@@ -189,8 +198,12 @@ def new_model?
     @new_model
   end
 
-  def changed_children?
-    @changed_children
+  def changed_nested_children?
+    @changed_nested_children
+  end
+
+  def changed_referenced_children?
+    @changed_referenced_children
   end
 
   def serialize_view(json, serialize_context: self.class.new_serialize_context)
@@ -202,9 +215,7 @@ def serialize_view(json, serialize_context: self.class.new_serialize_context)
   end
 
   def serialize_members(json, serialize_context:)
-    self.class._members.each do |member_name, member_data|
-      next unless serialize_context.includes_member?(member_name, !member_data.optional?)
-
+    self.class._members.each do |member_name, _member_data|
       self.public_send("serialize_#{member_name}", json, serialize_context: serialize_context)
     end
   end
@@ -227,22 +238,29 @@ def attribute_changed!(attr_name)
     @changed_attributes << attr_name.to_s
   end
 
-  def children_changed!
-    @changed_children = true
+  def nested_children_changed!
+    @changed_nested_children = true
+  end
+
+  def referenced_children_changed!
+    @changed_referenced_children = true
   end
 
   def changes
     ViewModel::Changes.new(
-      new:                new_model?,
-      changed_attributes: changed_attributes,
-      changed_children:   changed_children?)
+      new:                         new_model?,
+      changed_attributes:          changed_attributes,
+      changed_nested_children:     changed_nested_children?,
+      changed_referenced_children: changed_referenced_children?,
+    )
   end
 
   def clear_changes!
-    @previous_changes   = changes
-    @new_model          = false
-    @changed_attributes = []
-    @changed_children   = false
+    @previous_changes           = changes
+    @new_model                  = false
+    @changed_attributes         = []
+    @changed_nested_children    = false
+    @changed_referenced_children = false
     previous_changes
   end
 
@@ -348,9 +366,11 @@ def _deserialize_attribute(attr_data, serialized_value, references:, deserialize
       model.public_send("#{attr_data.model_attr_name}=", value)
     end
 
-    if attr_data.using_viewmodel? &&
-       Array.wrap(value).any? { |v| v.respond_to?(:previous_changes) && v.previous_changes.changed_tree? }
-      self.children_changed!
+    if attr_data.using_viewmodel?
+      previous_changes = Array.wrap(value).select { |v| v.respond_to?(:previous_changes) }.map!(&:previous_changes)
+
+      self.nested_children_changed!     if previous_changes.any? { |pc| pc.changed_nested_tree? }
+      self.referenced_children_changed! if previous_changes.any? { |pc| pc.changed_referenced_children? }
     end
   end
 
diff --git a/lib/view_model/record/attribute_data.rb b/lib/view_model/record/attribute_data.rb
index 14a4a375..37582f72 100644
--- a/lib/view_model/record/attribute_data.rb
+++ b/lib/view_model/record/attribute_data.rb
@@ -3,23 +3,28 @@
 class ViewModel::Record::AttributeData
   attr_reader :name, :model_attr_name, :attribute_viewmodel, :attribute_serializer
 
-  def initialize(name, model_attr_name, attribute_viewmodel, attribute_serializer, array, optional, read_only, write_once)
+  def initialize(name:,
+                 model_attr_name:,
+                 attribute_viewmodel:,
+                 attribute_serializer:,
+                 array:,
+                 read_only:,
+                 write_once:)
     @name                 = name
     @model_attr_name      = model_attr_name
     @attribute_viewmodel  = attribute_viewmodel
     @attribute_serializer = attribute_serializer
     @array                = array
-    @optional             = optional
     @read_only            = read_only
     @write_once           = write_once
   end
 
-  def array?
-    @array
+  def association?
+    false
   end
 
-  def optional?
-    @optional
+  def array?
+    @array
   end
 
   def read_only?
diff --git a/lib/view_model/serialize_context.rb b/lib/view_model/serialize_context.rb
index 61ac18a5..5d08cb06 100644
--- a/lib/view_model/serialize_context.rb
+++ b/lib/view_model/serialize_context.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'active_support/core_ext'
 require 'view_model/traversal_context'
 
@@ -17,52 +19,6 @@ def self.shared_context_class
   end
 
   delegate :references, :flatten_references, to: :shared_context
-
-  attr_reader :include, :prune
-
-  def initialize(include: nil, prune: nil, **rest)
-    super(**rest)
-    @include = self.class.normalize_includes(include)
-    @prune   = self.class.normalize_includes(prune)
-  end
-
-  def initialize_as_child(include:, prune:, **rest)
-    super(**rest)
-    @include = include
-    @prune   = prune
-  end
-
-  def for_child(parent_viewmodel, association_name:, **rest)
-    super(parent_viewmodel,
-          association_name: association_name,
-          include: @include.try { |i| i[association_name] },
-          prune:   @prune.try   { |p| p[association_name] },
-          **rest)
-  end
-
-  def includes_member?(member_name, default)
-    member_name = member_name.to_s
-
-    # Every node in the include tree is to be included
-    included = @include.try { |is| is.has_key?(member_name) }
-    # whereas only the leaves of the prune tree are to be removed
-    pruned   = @prune.try { |ps| ps.fetch(member_name, :sentinel).nil? }
-
-    (default || included) && !pruned
-  end
-
-  def add_includes(includes)
-    return if includes.blank?
-    @include ||= {}
-    @include.deep_merge!(self.class.normalize_includes(includes))
-  end
-
-  def add_prunes(prunes)
-    return if prunes.blank?
-    @prune ||= {}
-    @prune.deep_merge!(self.class.normalize_includes(prunes))
-  end
-
   delegate :add_reference, :has_references?, to: :references
 
   # Return viewmodels referenced during serialization and clear @references.
@@ -98,21 +54,4 @@ def serialize_references(json)
   def serialize_references_to_hash
     Jbuilder.new { |json| serialize_references(json) }.attributes!
   end
-
-  def self.normalize_includes(includes)
-    case includes
-    when Array
-      includes.each_with_object({}) do |v, new_includes|
-        new_includes.merge!(normalize_includes(v))
-      end
-    when Hash
-      includes.each_with_object({}) do |(k,v), new_includes|
-        new_includes[k.to_s] = normalize_includes(v)
-      end
-    when nil
-      nil
-    else
-      { includes.to_s => nil }
-    end
-  end
 end
diff --git a/shell.nix b/shell.nix
index 2890df23..8b840064 100644
--- a/shell.nix
+++ b/shell.nix
@@ -1,7 +1,7 @@
 with import <nixpkgs> {};
 
 (bundlerEnv {
-  name = "dev";
+  name = "iknow-view-models-shell";
   gemdir = ./nix/gem;
 
   gemConfig = (defaultGemConfig.override { postgresql = postgresql_11; });
diff --git a/test/helpers/arvm_test_utilities.rb b/test/helpers/arvm_test_utilities.rb
index 4dbed66a..4a957a7c 100644
--- a/test/helpers/arvm_test_utilities.rb
+++ b/test/helpers/arvm_test_utilities.rb
@@ -4,6 +4,12 @@
 require 'view_model'
 require 'view_model/test_helpers'
 
+unless ViewModel::Config.configured?
+  ViewModel::Config.configure! do
+    debug_deserialization true
+  end
+end
+
 require_relative 'query_logging.rb'
 
 ActiveSupport::TestCase.include(Minitest::Hooks)
diff --git a/test/helpers/controller_test_helpers.rb b/test/helpers/controller_test_helpers.rb
index 69885837..626a7dbb 100644
--- a/test/helpers/controller_test_helpers.rb
+++ b/test/helpers/controller_test_helpers.rb
@@ -33,6 +33,7 @@ def before_all
         has_many :parents
       end
       define_viewmodel do
+        root!
         attributes :name
       end
     end
@@ -77,11 +78,12 @@ def before_all
         belongs_to :category
       end
       define_viewmodel do
+        root!
         attributes   :name
         associations :label, :target
-        association  :children, optional: true
+        association  :children
         association  :poly, viewmodels: [:PolyOne, :PolyTwo]
-        association  :category, shared: true
+        association  :category, external: true
       end
     end
 
@@ -99,7 +101,7 @@ def before_all
       define_model do
         belongs_to :parent, inverse_of: :children
         acts_as_manual_list scope: :parent
-        validates :age, numericality: {less_than: 42}, allow_nil: true
+        validates :age, numericality: { less_than: 42 }, allow_nil: true
       end
       define_viewmodel do
         attributes :name, :age
diff --git a/test/helpers/viewmodel_spec_helpers.rb b/test/helpers/viewmodel_spec_helpers.rb
index 1d1fc2c8..43fb38c5 100644
--- a/test/helpers/viewmodel_spec_helpers.rb
+++ b/test/helpers/viewmodel_spec_helpers.rb
@@ -77,7 +77,7 @@ def model_attributes
       ViewModel::TestHelpers::ARVMBuilder::Spec.new(
         schema:    ->(t) { t.string :name },
         model:     ->(m) {},
-        viewmodel: ->(v) { attribute :name }
+        viewmodel: ->(v) { root!; attribute :name }
       )
     end
 
@@ -99,6 +99,10 @@ def subject_association
       raise RuntimeError.new('Test model does not have a child association')
     end
 
+    def subject_association_features
+      {}
+    end
+
     def subject_association_name
       subject_association.association_name
     end
@@ -114,9 +118,10 @@ module ParentAndBelongsToChild
     include ViewModelSpecHelpers::Base
 
     def model_attributes
+      f = subject_association_features
       super.merge(schema:    ->(t) { t.references :child, foreign_key: true },
                   model:     ->(m) { belongs_to :child, inverse_of: :model, dependent: :destroy },
-                  viewmodel: ->(v) { association :child })
+                  viewmodel: ->(v) { association :child, **f })
     end
 
     def child_attributes
@@ -134,17 +139,33 @@ def subject_association
     end
   end
 
+  module ParentAndSharedBelongsToChild
+    extend ActiveSupport::Concern
+    include ViewModelSpecHelpers::ParentAndBelongsToChild
+    def child_attributes
+      super.merge(viewmodel: ->(v) { root! })
+    end
+  end
+
   module List
     extend ActiveSupport::Concern
     include ViewModelSpecHelpers::Base
 
     def model_attributes
-      super.merge(schema:    ->(t) { t.integer :next_id },
-                  model:     ->(m) {
-                    belongs_to :next, class_name: self.name, inverse_of: :previous, dependent: :destroy
-                    has_one :previous, class_name: self.name, foreign_key: :next_id, inverse_of: :next
-                  },
-                  viewmodel: ->(v) { association :next })
+      ViewModel::TestHelpers::ARVMBuilder::Spec.new(
+        schema:    ->(t) {
+          t.string :name
+          t.integer :next_id
+        },
+        model:     ->(m) {
+          belongs_to :next, class_name: self.name, inverse_of: :previous, dependent: :destroy
+          has_one :previous, class_name: self.name, foreign_key: :next_id, inverse_of: :next
+        },
+        viewmodel: ->(v) {
+          # Not a root
+          association :next
+          attribute :name
+        })
     end
 
     def subject_association
@@ -157,9 +178,10 @@ module ParentAndHasOneChild
     include ViewModelSpecHelpers::Base
 
     def model_attributes
+      f = subject_association_features
       super.merge(
         model:     ->(m) { has_one :child, inverse_of: :model, dependent: :destroy },
-        viewmodel: ->(v) { association :child }
+        viewmodel: ->(v) { association :child, **f }
       )
     end
 
@@ -181,14 +203,23 @@ def subject_association
     end
   end
 
+  module ParentAndReferencedHasOneChild
+    extend ActiveSupport::Concern
+    include ViewModelSpecHelpers::ParentAndHasOneChild
+    def child_attributes
+      super.merge(viewmodel: ->(v) { root! })
+    end
+  end
+
   module ParentAndHasManyChildren
     extend ActiveSupport::Concern
     include ViewModelSpecHelpers::Base
 
     def model_attributes
+      f = subject_association_features
       super.merge(
         model:     ->(m) { has_many :children, inverse_of: :model, dependent: :destroy },
-        viewmodel: ->(v) { association :children }
+        viewmodel: ->(v) { association :children, **f }
       )
     end
 
@@ -210,22 +241,23 @@ def subject_association
     end
   end
 
-  module ParentAndOrderedChildren
+  module ParentAndSharedHasManyChildren
     extend ActiveSupport::Concern
-    include ViewModelSpecHelpers::Base
-
-    def model_attributes
-      super.merge(
-        model:     ->(m) { has_many :children, inverse_of: :model, dependent: :destroy },
-        viewmodel: ->(v) { association :children },
-      )
+    include ViewModelSpecHelpers::ParentAndHasManyChildren
+    def child_attributes
+      super.merge(viewmodel: ->(v) { root! })
     end
+  end
+
+  module ParentAndOrderedChildren
+    extend ActiveSupport::Concern
+    include ViewModelSpecHelpers::ParentAndHasManyChildren
 
     def child_attributes
       super.merge(
-        schema:    ->(t) { t.references :model, foreign_key: true; t.float :position, null: false },
-        model:     ->(m) { belongs_to :model, inverse_of: :children },
-        viewmodel: ->(v) { acts_as_list :position },
+        schema:    ->(t) { t.float :position, null: false },
+        model:     ->(_m) { acts_as_manual_list scope: :model },
+        viewmodel: ->(_v) { acts_as_list :position },
       )
     end
 
@@ -233,7 +265,7 @@ def child_viewmodel_class
       # child depends on parent, ensure it's touched first
       viewmodel_class
 
-      # Add a deferrable unique position constraiont
+      # Add a deferrable unique position constraint
       super do |klass|
         model = klass.model_class
         table = model.table_name
@@ -242,38 +274,15 @@ def child_viewmodel_class
           SQL
       end
     end
-
-    def subject_association
-      viewmodel_class._association_data('children')
-    end
   end
 
-  module ParentAndSharedChild
-    extend ActiveSupport::Concern
-    include ViewModelSpecHelpers::Base
 
-    def model_attributes
-      super.merge(
-        schema:    ->(t) { t.references :child, foreign_key: true },
-        model:     ->(m) { belongs_to :child, inverse_of: :model, dependent: :destroy },
-        viewmodel: ->(v) { association :child, shared: true }
-      )
-    end
-
-    def child_attributes
-      super.merge(
-        model: ->(m) { has_one :model, inverse_of: :child }
-      )
-    end
-
-    # parent depends on child, ensure it's touched first
-    def viewmodel_class
-      child_viewmodel_class
-      super
-    end
+  module ParentAndExternalSharedChild
+    extend ActiveSupport::Concern
+    include ViewModelSpecHelpers::ParentAndSharedBelongsToChild
 
-    def subject_association
-      viewmodel_class._association_data('child')
+    def subject_association_features
+      { external: true }
     end
   end
 
@@ -282,15 +291,17 @@ module ParentAndHasManyThroughChildren
     include ViewModelSpecHelpers::Base
 
     def model_attributes
+      f = subject_association_features
       super.merge(
         model:     ->(m) { has_many :model_children, inverse_of: :model, dependent: :destroy },
-        viewmodel: ->(v) { association :children, shared: true, through: :model_children, through_order_attr: :position }
+        viewmodel: ->(v) { association :children, through: :model_children, through_order_attr: :position, **f }
       )
     end
 
     def child_attributes
       super.merge(
-        model: ->(m) { has_many :model_children, inverse_of: :child, dependent: :destroy }
+        model: ->(m) { has_many :model_children, inverse_of: :child, dependent: :destroy },
+        viewmodel: ->(v) { root! }
       )
     end
 
diff --git a/test/unit/view_model/access_control_test.rb b/test/unit/view_model/access_control_test.rb
index 1b35dcb6..d80dd8e3 100644
--- a/test/unit/view_model/access_control_test.rb
+++ b/test/unit/view_model/access_control_test.rb
@@ -190,6 +190,7 @@ def before_all
         end
 
         define_viewmodel do
+          root!
           attribute   :val
           association :tree2
 
@@ -215,7 +216,7 @@ def self.new_deserialize_context(**args)
 
         define_viewmodel do
           attribute   :val
-          association :tree1, shared: true, optional: false
+          association :tree1
         end
       end
     end
@@ -447,15 +448,16 @@ class ChangeTrackingTest < ActiveSupport::TestCase
     include ViewModelSpecHelpers::List
     extend Minitest::Spec::DSL
 
-    def assert_changes_match(changes, new, deleted, children, attributes, associations)
+    def assert_changes_match(changes, n: false, d: false, nstc: false, refc: false, att: [], ass: [])
       assert_equal(
         changes,
         ViewModel::Changes.new(
-          new: new,
-          deleted: deleted,
-          changed_children: children,
-          changed_attributes: attributes,
-          changed_associations: associations))
+          new: n,
+          deleted: d,
+          changed_nested_children: nstc,
+          changed_referenced_children: refc,
+          changed_attributes: att,
+          changed_associations: ass))
     end
 
     describe 'with parent and points-to child test models' do
@@ -479,7 +481,7 @@ def new_model_with_child
         vm = viewmodel_class.deserialize_from_view(view, deserialize_context: ctx)
 
         vm_changes = ctx.valid_edit_changes(vm.to_reference)
-        assert_changes_match(vm_changes, true, false, false, ['name'], [])
+        assert_changes_match(vm_changes, n: true, att: ['name'])
       end
 
       it 'records a destroyed model' do
@@ -489,7 +491,7 @@ def new_model_with_child
         vm.destroy!(deserialize_context: ctx)
 
         vm_changes = ctx.valid_edit_changes(vm.to_reference)
-        assert_changes_match(vm_changes, false, true, false, [], [])
+        assert_changes_match(vm_changes, d: true)
       end
 
       it 'records a change to an attribute' do
@@ -498,7 +500,7 @@ def new_model_with_child
         end
 
         vm_changes = ctx.valid_edit_changes(vm.to_reference)
-        assert_changes_match(vm_changes, false, false, false, ['name'], [])
+        assert_changes_match(vm_changes, att: ['name'])
       end
 
       it 'records a new child' do
@@ -507,10 +509,10 @@ def new_model_with_child
         end
 
         vm_changes = ctx.valid_edit_changes(vm.to_reference)
-        assert_changes_match(vm_changes, false, false, true, [], ['child'])
+        assert_changes_match(vm_changes, nstc: true, ass: ['child'])
 
         c_changes = ctx.valid_edit_changes(vm.child.to_reference)
-        assert_changes_match(c_changes, true, false, false, ['name'], [])
+        assert_changes_match(c_changes, n: true, att: ['name'])
       end
 
       it 'records a replaced child' do
@@ -522,14 +524,14 @@ def new_model_with_child
         end
 
         vm_changes = ctx.valid_edit_changes(vm.to_reference)
-        assert_changes_match(vm_changes, false, false, true, [], ['child'])
+        assert_changes_match(vm_changes, nstc: true, ass: ['child'])
 
         c_changes = ctx.valid_edit_changes(vm.child.to_reference)
-        assert_changes_match(c_changes, true, false, false, ['name'], [])
+        assert_changes_match(c_changes, n: true, att: ['name'])
 
         oc_changes = ctx.valid_edit_changes(
           ViewModel::Reference.new(child_viewmodel_class, old_child.id))
-        assert_changes_match(oc_changes, false, true, false, [], [])
+        assert_changes_match(oc_changes, d: true)
       end
 
       it 'records an edited child' do
@@ -542,10 +544,10 @@ def new_model_with_child
         # The parent node itself wasn't changed, so must not have been
         # valid_edit checked
         refute(ctx.was_edited?(vm.to_reference))
-        assert_changes_match(vm.previous_changes, false, false, true, [], [])
+        assert_changes_match(vm.previous_changes, nstc: true)
 
         c_changes = ctx.valid_edit_changes(vm.child.to_reference)
-        assert_changes_match(c_changes, false, false, false, ['name'], [])
+        assert_changes_match(c_changes, att: ['name'])
       end
 
       it 'records a deleted child' do
@@ -557,11 +559,11 @@ def new_model_with_child
         end
 
         vm_changes = ctx.valid_edit_changes(vm.to_reference)
-        assert_changes_match(vm_changes, false, false, true, [], ['child'])
+        assert_changes_match(vm_changes, nstc: true, ass: ['child'])
 
         oc_changes = ctx.valid_edit_changes(
           ViewModel::Reference.new(child_viewmodel_class, old_child.id))
-        assert_changes_match(oc_changes, false, true, false, [], [])
+        assert_changes_match(oc_changes, d: true)
       end
     end
 
@@ -585,7 +587,7 @@ def new_model
         end
 
         vm_changes = ctx.valid_edit_changes(vm.to_reference)
-        assert_changes_match(vm_changes, false, false, true, [], ['children'])
+        assert_changes_match(vm_changes, nstc: true, ass: ['children'])
 
         new_children, existing_children = vm.children.partition do |c|
           c.name < 'm'
@@ -593,7 +595,7 @@ def new_model
 
         new_children.each do |c|
           c_changes = ctx.valid_edit_changes(c.to_reference)
-          assert_changes_match(c_changes, true, false, false, ['name'], [])
+          assert_changes_match(c_changes, n: true, att: ['name'])
         end
 
         existing_children.each do |c|
@@ -613,15 +615,15 @@ def new_model
         refute(vm.children.include?(replaced_child))
 
         vm_changes = ctx.valid_edit_changes(vm.to_reference)
-        assert_changes_match(vm_changes, false, false, true, [], ['children'])
+        assert_changes_match(vm_changes, nstc: true, ass: ['children'])
 
         new_child = vm.children.detect { |c| c.name == 'b' }
         c_changes = ctx.valid_edit_changes(new_child.to_reference)
-        assert_changes_match(c_changes, true, false, false, ['name'], [])
+        assert_changes_match(c_changes, n:true, att: ['name'])
 
         oc_changes = ctx.valid_edit_changes(
           ViewModel::Reference.new(child_viewmodel_class, replaced_child.id))
-        assert_changes_match(oc_changes, false, true, false, [], [])
+        assert_changes_match(oc_changes, d: true)
       end
 
       it 'records reordered children' do
@@ -630,7 +632,7 @@ def new_model
         end
 
         vm_changes = ctx.valid_edit_changes(vm.to_reference)
-        assert_changes_match(vm_changes, false, false, false, [], ['children'])
+        assert_changes_match(vm_changes, ass: ['children'])
 
         vm.children.each do |c|
           refute(ctx.was_edited?(c.to_reference))
@@ -639,23 +641,23 @@ def new_model
     end
 
     describe 'with parent and shared child test models' do
-      include ViewModelSpecHelpers::ParentAndSharedChild
+      include ViewModelSpecHelpers::ParentAndSharedBelongsToChild
 
       def new_model
         model_class.new(name: 'a', child: child_model_class.new(name: 'z'))
       end
 
-      it 'records an change to child without a tree change' do
+      it 'records a change to child without a tree change' do
         vm, ctx = alter_by_view!(viewmodel_class, create_model!) do |view, refs|
           view['child'] = { '_ref' => 'cref' }
           refs.clear['cref'] = { '_type' => child_view_name, 'name' => 'b' }
         end
 
         vm_changes = ctx.valid_edit_changes(vm.to_reference)
-        assert_changes_match(vm_changes, false, false, false, [], ['child'])
+        assert_changes_match(vm_changes, ass: ['child'])
 
         c_changes = ctx.valid_edit_changes(vm.child.to_reference)
-        assert_changes_match(c_changes, true, false, false, ['name'], [])
+        assert_changes_match(c_changes, n: true, att: ['name'])
       end
 
       it 'records an edited child without a tree change' do
@@ -664,10 +666,10 @@ def new_model
         end
 
         refute(ctx.was_edited?(vm.to_reference))
-        assert_changes_match(vm.previous_changes, false, false, false, [], [])
+        assert_changes_match(vm.previous_changes)
 
         c_changes = ctx.valid_edit_changes(vm.child.to_reference)
-        assert_changes_match(c_changes, false, false, false, ['name'], [])
+        assert_changes_match(c_changes, att: ['name'])
       end
 
       it 'records a deleted child' do
@@ -680,12 +682,61 @@ def new_model
         end
 
         vm_changes = ctx.valid_edit_changes(vm.to_reference)
-        assert_changes_match(vm_changes, false, false, false, [], ['child'])
+        assert_changes_match(vm_changes, ass: ['child'])
 
         refute(ctx.was_edited?(old_child.to_reference))
       end
     end
 
+    describe 'with parent and owned referenced child test models' do
+      include ViewModelSpecHelpers::ParentAndReferencedHasOneChild
+
+      def new_model
+        model_class.new(name: 'a', child: child_model_class.new(name: 'z'))
+      end
+
+      it 'records a change to child with referenced tree change' do
+        vm, ctx = alter_by_view!(viewmodel_class, create_model!) do |view, refs|
+          view['child'] = { '_ref' => 'cref' }
+          refs.clear['cref'] = { '_type' => child_view_name, 'name' => 'b' }
+        end
+
+        vm_changes = ctx.valid_edit_changes(vm.to_reference)
+        assert_changes_match(vm_changes, refc: true, ass: ['child'])
+
+        c_changes = ctx.valid_edit_changes(vm.child.to_reference)
+        assert_changes_match(c_changes, n: true, att: ['name'])
+      end
+
+      it 'records an edited child with referenced tree change' do
+        vm, ctx = alter_by_view!(viewmodel_class, create_model!) do |_view, refs|
+          refs.values.first.merge!('name' => 'b')
+        end
+
+        refute(ctx.was_edited?(vm.to_reference))
+        assert_changes_match(vm.previous_changes, refc: true)
+
+        c_changes = ctx.valid_edit_changes(vm.child.to_reference)
+        assert_changes_match(c_changes, att: ['name'])
+      end
+
+      it 'records a deleted child' do
+        vm = create_viewmodel!
+        old_child = vm.child
+
+        vm, ctx = alter_by_view!(viewmodel_class, vm.model) do |view, refs|
+          view['child'] = nil
+          refs.clear
+        end
+
+        vm_changes = ctx.valid_edit_changes(vm.to_reference)
+        assert_changes_match(vm_changes, refc: true, ass: ['child'])
+
+        c_changes = ctx.valid_edit_changes(old_child.to_reference)
+        assert_changes_match(c_changes, d: true)
+      end
+    end
+
     describe 'with has_many_through children test models' do
       include ViewModelSpecHelpers::ParentAndHasManyThroughChildren
 
@@ -706,7 +757,7 @@ def new_model
         end
 
         vm_changes = ctx.valid_edit_changes(vm.to_reference)
-        assert_changes_match(vm_changes, false, false, false, [], ['children'])
+        assert_changes_match(vm_changes, ass: ['children'])
 
         new_children, existing_children = vm.children.partition do |c|
           c.name < 'm'
@@ -714,7 +765,7 @@ def new_model
 
         new_children.each do |c|
           c_changes = ctx.valid_edit_changes(c.to_reference)
-          assert_changes_match(c_changes, true, false, false, ['name'], [])
+          assert_changes_match(c_changes, n: true, att: ['name'])
         end
 
         existing_children.each do |c|
@@ -734,7 +785,7 @@ def new_model
         end
 
         vm_changes = ctx.valid_edit_changes(vm.to_reference)
-        assert_changes_match(vm_changes, false, false, false, [], ['children'])
+        assert_changes_match(vm_changes, ass: ['children'])
 
         new_children, existing_children = vm.children.partition do |c|
           c.name < 'm'
@@ -742,7 +793,7 @@ def new_model
 
         new_children.each do |c|
           c_changes = ctx.valid_edit_changes(c.to_reference)
-          assert_changes_match(c_changes, true, false, false, ['name'], [])
+          assert_changes_match(c_changes, n: true, att: ['name'])
         end
 
         existing_children.each do |c|
@@ -758,7 +809,7 @@ def new_model
         end
 
         vm_changes = ctx.valid_edit_changes(vm.to_reference)
-        assert_changes_match(vm_changes, false, false, false, [], ['children'])
+        assert_changes_match(vm_changes, ass: ['children'])
 
         vm.children.each do |c|
           refute(ctx.was_edited?(c.to_reference))
diff --git a/test/unit/view_model/active_record/belongs_to_test.rb b/test/unit/view_model/active_record/belongs_to_test.rb
index 22034e82..356e870c 100644
--- a/test/unit/view_model/active_record/belongs_to_test.rb
+++ b/test/unit/view_model/active_record/belongs_to_test.rb
@@ -1,5 +1,6 @@
 require_relative "../../../helpers/arvm_test_utilities.rb"
 require_relative "../../../helpers/arvm_test_models.rb"
+require_relative '../../../helpers/viewmodel_spec_helpers.rb'
 
 require "minitest/autorun"
 
@@ -7,122 +8,57 @@
 
 class ViewModel::ActiveRecord::BelongsToTest < ActiveSupport::TestCase
   include ARVMTestUtilities
-
-  module WithLabel
-    def before_all
-      super
-
-      build_viewmodel(:Label) do
-        define_schema do |t|
-          t.string :text
-        end
-
-        define_model do
-          has_one :parent, inverse_of: :label
-        end
-
-        define_viewmodel do
-          attributes :text
-        end
-      end
-    end
-  end
-
-  module WithParent
-    def before_all
-      super
-
-      build_viewmodel(:Parent) do
-        define_schema do |t|
-          t.string :name
-          t.references :label, foreign_key: true
-        end
-
-        define_model do
-          belongs_to :label, inverse_of: :parent, dependent: :destroy
-        end
-
-        define_viewmodel do
-          attributes   :name
-          associations :label
-        end
-      end
-    end
-  end
-
-  module WithOwner
-    def before_all
-      super
-
-      build_viewmodel(:Owner) do
-        define_schema do |t|
-          t.integer :deleted_id
-          t.integer :ignored_id
-        end
-
-        define_model do
-          belongs_to :deleted, class_name: Label.name, dependent: :delete
-          belongs_to :ignored, class_name: Label.name
-        end
-
-        define_viewmodel do
-          associations :deleted, :ignored
-        end
-      end
-    end
-  end
-
-  include WithLabel
-  include WithParent
+  extend Minitest::Spec::DSL
+  include ViewModelSpecHelpers::ParentAndBelongsToChild
 
   def setup
     super
 
     # TODO make a `has_list?` that allows a parent to set all children as an array
-    @parent1 = Parent.new(name: "p1",
-                          label: Label.new(text: "p1l"))
-    @parent1.save!
+    @model1 = model_class.new(name: "p1",
+                              child: child_model_class.new(name: "p1l"))
+    @model1.save!
 
-    @parent2 = Parent.new(name: "p2",
-                          label: Label.new(text: "p2l"))
+    @model2 = model_class.new(name: "p2",
+                              child: child_model_class.new(name: "p2l"))
 
-    @parent2.save!
+    @model2.save!
 
     enable_logging!
   end
 
   def test_serialize_view
-    view, _refs = serialize_with_references(ParentView.new(@parent1))
+    view, _refs = serialize_with_references(ModelView.new(@model1))
 
-    assert_equal({ "_type"    => "Parent",
+    assert_equal({ "_type"    => "Model",
                    "_version" => 1,
-                   "id"       => @parent1.id,
-                   "name"     => @parent1.name,
-                   "label"    => { "_type"    => "Label",
+                   "id"       => @model1.id,
+                   "name"     => @model1.name,
+                   "child"    => { "_type"    => "Child",
                                    "_version" => 1,
-                                   "id"       => @parent1.label.id,
-                                   "text"     => @parent1.label.text },
+                                   "id"       => @model1.child.id,
+                                   "name"     => @model1.child.name },
                  },
                  view)
   end
 
   def test_loading_batching
     log_queries do
-      serialize(ParentView.load)
+      serialize(ModelView.load)
     end
 
-    assert_equal(['Parent Load', 'Label Load'],
+    assert_equal(['Model Load', 'Child Load'],
                  logged_load_queries)
   end
 
   def test_create_from_view
     view = {
-      "_type"    => "Parent",
+      "_type"    => "Model",
       "name"     => "p",
-      "label"    => { "_type" => "Label", "text" => "l" },
+      "child"    => { "_type" => "Child", "name" => "l" },
     }
 
-    pv = ParentView.deserialize_from_view(view)
+    pv = ModelView.deserialize_from_view(view)
     p = pv.model
 
     assert(!p.changed?)
@@ -130,185 +66,181 @@ def test_create_from_view
 
     assert_equal("p", p.name)
 
-    assert(p.label.present?)
-    assert_equal("l", p.label.text)
+    assert(p.child.present?)
+    assert_equal("l", p.child.name)
   end
 
   def test_create_belongs_to_nil
-    view = { '_type' => 'Parent', 'name' => 'p', 'label' => nil }
-    pv = ParentView.deserialize_from_view(view)
-    assert_nil(pv.model.label)
+    view = { '_type' => 'Model', 'name' => 'p', 'child' => nil }
+    pv = ModelView.deserialize_from_view(view)
+    assert_nil(pv.model.child)
   end
 
   def test_create_invalid_child_type
-    view = { '_type' => 'Parent', 'name' => 'p', 'label' => { '_type' => 'Parent', 'name' => 'q' } }
+    view = { '_type' => 'Model', 'name' => 'p', 'child' => { '_type' => 'Model', 'name' => 'q' } }
     assert_raises(ViewModel::DeserializationError::InvalidAssociationType) do
-      ParentView.deserialize_from_view(view)
+      ModelView.deserialize_from_view(view)
     end
   end
 
   def test_belongs_to_create
-    @parent1.update(label: nil)
+    @model1.update(child: nil)
 
-    alter_by_view!(ParentView, @parent1) do |view, refs|
-      view['label'] = { '_type' => 'Label', 'text' => 'cheese' }
+    alter_by_view!(ModelView, @model1) do |view, refs|
+      view['child'] = { '_type' => 'Child', 'name' => 'cheese' }
     end
 
-    assert_equal('cheese', @parent1.label.text)
+    assert_equal('cheese', @model1.child.name)
   end
 
   def test_belongs_to_replace
-    old_label = @parent1.label
+    old_child = @model1.child
 
-    alter_by_view!(ParentView, @parent1) do |view, refs|
-      view['label'] = { '_type' => 'Label', 'text' => 'cheese' }
+    alter_by_view!(ModelView, @model1) do |view, refs|
+      view['child'] = { '_type' => 'Child', 'name' => 'cheese' }
     end
 
-    assert_equal('cheese', @parent1.label.text)
-    assert(Label.where(id: old_label).blank?)
+    assert_equal('cheese', @model1.child.name)
+    assert(Child.where(id: old_child).blank?)
   end
 
   def test_belongs_to_move_and_replace
-    old_p1_label = @parent1.label
-    old_p2_label = @parent2.label
+    old_p1_child = @model1.child
+    old_p2_child = @model2.child
 
-    set_by_view!(ParentView, [@parent1, @parent2]) do |(p1, p2), refs|
-      p1['label'] = nil
-      p2['label'] = update_hash_for(LabelView, old_p1_label)
+    set_by_view!(ModelView, [@model1, @model2]) do |(p1, p2), refs|
+      p1['child'] = nil
+      p2['child'] = update_hash_for(ChildView, old_p1_child)
     end
 
-    assert(@parent1.label.blank?, 'l1 label reference removed')
-    assert_equal(old_p1_label, @parent2.label, 'p2 has label from p1')
-    assert(Label.where(id: old_p2_label).blank?, 'p2 old label deleted')
+    assert(@model1.child.blank?, 'l1 child reference removed')
+    assert_equal(old_p1_child, @model2.child, 'p2 has child from p1')
+    assert(Child.where(id: old_p2_child).blank?, 'p2 old child deleted')
   end
 
   def test_belongs_to_swap
-    old_p1_label = @parent1.label
-    old_p2_label = @parent2.label
+    old_p1_child = @model1.child
+    old_p2_child = @model2.child
 
-    alter_by_view!(ParentView, [@parent1, @parent2]) do |(p1, p2), refs|
-      p1['label'] = update_hash_for(LabelView, old_p2_label)
-      p2['label'] = update_hash_for(LabelView, old_p1_label)
+    alter_by_view!(ModelView, [@model1, @model2]) do |(p1, p2), refs|
+      p1['child'] = update_hash_for(ChildView, old_p2_child)
+      p2['child'] = update_hash_for(ChildView, old_p1_child)
     end
 
-    assert_equal(old_p2_label, @parent1.label, 'p1 has label from p2')
-    assert_equal(old_p1_label, @parent2.label, 'p2 has label from p1')
+    assert_equal(old_p2_child, @model1.child, 'p1 has child from p2')
+    assert_equal(old_p1_child, @model2.child, 'p2 has child from p1')
   end
 
   def test_moved_child_is_not_delete_checked
     # move from p1 to p3
-    d_context = ParentView.new_deserialize_context
+    d_context = ModelView.new_deserialize_context
 
-    target_label = Label.create
-    from_parent  = Parent.create(name: 'from', label: target_label)
-    to_parent    = Parent.create(name: 'p3')
+    target_child = Child.create
+    from_model  = Model.create(name: 'from', child: target_child)
+    to_model    = Model.create(name: 'p3')
 
     alter_by_view!(
-      ParentView, [from_parent, to_parent],
+      ModelView, [from_model, to_model],
       deserialize_context: d_context
     ) do |(from, to), refs|
-      from['label'] = nil
-      to['label']   = update_hash_for(LabelView, target_label)
+      from['child'] = nil
+      to['child']   = update_hash_for(ChildView, target_child)
     end
 
-    assert_equal(target_label, to_parent.label, 'target label moved')
-    assert_equal([ViewModel::Reference.new(ParentView, from_parent.id),
-                  ViewModel::Reference.new(ParentView, to_parent.id)],
+    assert_equal(target_child, to_model.child, 'target child moved')
+    assert_equal([ViewModel::Reference.new(ModelView, from_model.id),
+                  ViewModel::Reference.new(ModelView, to_model.id)],
                  d_context.valid_edit_refs,
-                 "only parents are checked for change; child was not")
+                 "only models are checked for change; child was not")
   end
 
   def test_implicit_release_invalid_belongs_to
-    taken_label_ref = update_hash_for(LabelView, @parent1.label)
+    taken_child_ref = update_hash_for(ChildView, @model1.child)
     assert_raises(ViewModel::DeserializationError::ParentNotFound) do
-      ParentView.deserialize_from_view(
-        [{ '_type' => 'Parent',
+      ModelView.deserialize_from_view(
+        [{ '_type' => 'Model',
            'name'  => 'newp',
-           'label' => taken_label_ref }])
+           'child' => taken_child_ref }])
     end
   end
 
   class GCTests < ActiveSupport::TestCase
     include ARVMTestUtilities
-    include WithLabel
-    include WithOwner
-    include WithParent
+    include ViewModelSpecHelpers::ParentAndBelongsToChild
+
+    def model_attributes
+      super.merge(
+        schema: ->(t) do
+          t.integer :deleted_child_id
+          t.integer :ignored_child_id
+        end,
+        model: ->(m) do
+          belongs_to :deleted_child, class_name: Child.name, dependent: :delete
+          belongs_to :ignored_child, class_name: Child.name
+        end,
+        viewmodel: ->(v) do
+          associations :deleted_child, :ignored_child
+        end)
+    end
 
     # test belongs_to garbage collection - dependent: delete_all
     def test_gc_dependent_delete_all
-      owner = Owner.create(deleted: Label.new(text: 'one'))
-      old_label = owner.deleted
+      model = model_class.create(deleted_child: Child.new(name: 'one'))
+      old_child = model.deleted_child
 
-      alter_by_view!(OwnerView, owner) do |ov, refs|
-        ov['deleted'] = { '_type' => 'Label', 'text' => 'two' }
+      alter_by_view!(ModelView, model) do |ov, _refs|
+        ov['deleted_child'] = { '_type' => 'Child', 'name' => 'two' }
       end
 
-      assert_equal('two', owner.deleted.text)
-      refute_equal(old_label, owner.deleted)
-      assert(Label.where(id: old_label.id).blank?)
+      assert_equal('two', model.deleted_child.name)
+      refute_equal(old_child, model.deleted_child)
+      assert(Child.where(id: old_child.id).blank?)
     end
 
     def test_no_gc_dependent_ignore
-      owner = Owner.create(ignored: Label.new(text: "one"))
-      old_label = owner.ignored
+      model = model_class.create(ignored_child: Child.new(name: "one"))
+      old_child = model.ignored_child
 
-      alter_by_view!(OwnerView, owner) do |ov, refs|
-        ov['ignored'] = { '_type' => 'Label', 'text' => 'two' }
+      alter_by_view!(ModelView, model) do |ov, _refs|
+        ov['ignored_child'] = { '_type' => 'Child', 'name' => 'two' }
       end
-      assert_equal('two', owner.ignored.text)
-      refute_equal(old_label, owner.ignored)
-      assert_equal(1, Label.where(id: old_label.id).count)
+      assert_equal('two', model.ignored_child.name)
+      refute_equal(old_child, model.ignored_child)
+      assert_equal(1, Child.where(id: old_child.id).count)
     end
   end
 
   class RenamedTest < ActiveSupport::TestCase
     include ARVMTestUtilities
-    include WithLabel
-
-    def before_all
-      super
-
-      build_viewmodel(:Parent) do
-        define_schema do |t|
-          t.string :name
-          t.references :label, foreign_key: true
-        end
-
-        define_model do
-          belongs_to :label, inverse_of: :parent, dependent: :destroy
-        end
+    include ViewModelSpecHelpers::ParentAndBelongsToChild
 
-        define_viewmodel do
-          attributes :name
-          association :label, as: :something_else
-        end
-      end
+    def subject_association_features
+      { as: :something_else }
     end
 
     def setup
       super
 
-      @parent = Parent.create(name: 'p1', label: Label.new(text: 'l1'))
+      @model = model_class.create(name: 'p1', child: child_model_class.new(name: 'l1'))
 
       enable_logging!
     end
 
     def test_dependencies
-      root_updates, _ref_updates = ViewModel::ActiveRecord::UpdateData.parse_hashes([{ '_type' => 'Parent', 'something_else' => nil }])
-      assert_equal(DeepPreloader::Spec.new('label' => DeepPreloader::Spec.new), root_updates.first.preload_dependencies)
-      assert_equal({ 'something_else' => {} }, root_updates.first.updated_associations)
+      root_updates, _ref_updates = ViewModel::ActiveRecord::UpdateData.parse_hashes([{ '_type' => 'Model', 'something_else' => nil }])
+      assert_equal(DeepPreloader::Spec.new('child' => DeepPreloader::Spec.new), root_updates.first.preload_dependencies)
     end
 
     def test_renamed_roundtrip
-      alter_by_view!(ParentView, @parent) do |view, refs|
-        assert_equal({ 'id'       => @parent.label.id,
-                       '_type'    => 'Label',
+      alter_by_view!(ModelView, @model) do |view, refs|
+        assert_equal({ 'id'       => @model.child.id,
+                       '_type'    => 'Child',
                        '_version' => 1,
-                       'text'     => 'l1' },
+                       'name'     => 'l1' },
                      view['something_else'])
-        view['something_else']['text'] = 'new l1 text'
+        view['something_else']['name'] = 'new l1 name'
       end
-      assert_equal('new l1 text', @parent.label.text)
+      assert_equal('new l1 name', @model.child.name)
     end
   end
 
@@ -353,7 +285,7 @@ def before_all
     end
 
 
-    # Do we support replacing a node in the tree and reparenting its children
+    # Do we support replacing a node in the tree and remodeling its children
     # back to it? In theory we want to, but currently we don't: the child node
     # is unresolvable.
 
diff --git a/test/unit/view_model/active_record/cache_test.rb b/test/unit/view_model/active_record/cache_test.rb
index bf23c6f9..7781eee0 100644
--- a/test/unit/view_model/active_record/cache_test.rb
+++ b/test/unit/view_model/active_record/cache_test.rb
@@ -41,7 +41,7 @@ def model_attributes
           schema:    ->(t) { t.references :shared, foreign_key: true },
           model:     ->(_) { belongs_to :shared, inverse_of: :models },
           viewmodel: ->(_) {
-            association :shared, shared: true, optional: false
+            association :shared
             cacheable!
           }
         )
@@ -63,6 +63,7 @@ def shared_viewmodel_class
           end
 
           define_viewmodel do
+            root!
             attributes :name
             cacheable!(cache_group: shared_cache_group)
           end
@@ -326,7 +327,7 @@ def fetch_with_cache
     end
 
     describe "with a non-cacheable shared child" do
-      include ViewModelSpecHelpers::ParentAndSharedChild
+      include ViewModelSpecHelpers::ParentAndSharedBelongsToChild
       def model_attributes
         super.merge(viewmodel: ->(_) { cacheable! })
       end
diff --git a/test/unit/view_model/active_record/cloner_test.rb b/test/unit/view_model/active_record/cloner_test.rb
index 7d4cf63c..89c7c289 100644
--- a/test/unit/view_model/active_record/cloner_test.rb
+++ b/test/unit/view_model/active_record/cloner_test.rb
@@ -173,7 +173,7 @@ module BehavesLikeCloningAChild
       end
 
       describe "as belongs_to shared child" do
-        include ViewModelSpecHelpers::ParentAndSharedChild
+        include ViewModelSpecHelpers::ParentAndSharedBelongsToChild
         include BehavesLikeConstructingAChild
         it "can clone the model but not the child" do
             clone_model = Cloner.new.clone(viewmodel)
diff --git a/test/unit/view_model/active_record/controller_test.rb b/test/unit/view_model/active_record/controller_test.rb
index 52085f04..ca1f4159 100644
--- a/test/unit/view_model/active_record/controller_test.rb
+++ b/test/unit/view_model/active_record/controller_test.rb
@@ -1,15 +1,14 @@
 # -*- coding: utf-8 -*-
 
-require "bundler/setup"
-Bundler.require
-
-require_relative "../../../helpers/callback_tracer.rb"
-require_relative "../../../helpers/controller_test_helpers.rb"
-
-require 'byebug'
-
 require "minitest/autorun"
 require 'minitest/unit'
+require 'minitest/hooks'
+
+require "view_model"
+require "view_model/active_record"
+
+require_relative "../../../helpers/controller_test_helpers.rb"
+require_relative "../../../helpers/callback_tracer.rb"
 
 class ViewModel::ActiveRecord::ControllerTest < ActiveSupport::TestCase
   include ARVMTestUtilities
@@ -144,9 +143,7 @@ def test_create
     p2_view = ParentView.new(p2)
     assert(p2.present?, 'p2 created')
 
-    context = ParentView.new_serialize_context(include: 'children')
-    assert_equal({ 'data' => p2_view.to_hash(serialize_context: context) },
-                 parentcontroller.hash_response)
+    assert_equal({ 'data' => p2_view.to_hash }, parentcontroller.hash_response)
 
     assert_all_hooks_nested_inside_parent_hook(parentcontroller.hook_trace)
   end
@@ -331,6 +328,7 @@ def test_nested_collection_append_many
     assert_all_hooks_nested_inside_parent_hook(childcontroller.hook_trace)
   end
 
+  # FIXME: nested controllers really need to be to other roots; children aren't roots.
   def test_nested_collection_replace
     # Parent.children
     old_children = @parent.children
diff --git a/test/unit/view_model/active_record/has_many_test.rb b/test/unit/view_model/active_record/has_many_test.rb
index b89d26b0..cbe0fce3 100644
--- a/test/unit/view_model/active_record/has_many_test.rb
+++ b/test/unit/view_model/active_record/has_many_test.rb
@@ -1,5 +1,6 @@
 require_relative "../../../helpers/arvm_test_utilities.rb"
 require_relative "../../../helpers/arvm_test_models.rb"
+require_relative '../../../helpers/viewmodel_spec_helpers.rb'
 
 require "minitest/autorun"
 
@@ -8,69 +9,29 @@
 class ViewModel::ActiveRecord::HasManyTest < ActiveSupport::TestCase
   include ARVMTestUtilities
 
-  def self.build_parent(arvm_test_case)
-    arvm_test_case.build_viewmodel(:Parent) do
-      define_schema do |t|
-        t.string :name
-      end
-
-      define_model do
-        has_many :children, dependent: :destroy, inverse_of: :parent
-      end
-
-      define_viewmodel do
-        attributes :name
-        associations :children
-      end
-    end
-  end
-
-  def self.build_child(arvm_test_case)
-    arvm_test_case.build_viewmodel(:Child) do
-      define_schema do |t|
-        t.references :parent, null: false, foreign_key: true
-        t.string :name
-        t.float :position
-      end
-
-      define_model do
-        belongs_to :parent, inverse_of: :children
-        acts_as_manual_list scope: :parent
-      end
-
-      define_viewmodel do
-        attributes :name
-        acts_as_list :position
-      end
-    end
-
-  end
-
-  def before_all
-    self.class.build_parent(self)
-    self.class.build_child(self)
-  end
+  extend Minitest::Spec::DSL
+  include ViewModelSpecHelpers::ParentAndOrderedChildren
 
   def setup
     super
 
-    @parent1 = Parent.new(name: "p1",
-                          children: [Child.new(name: "p1c1", position: 1),
-                                     Child.new(name: "p1c2", position: 2),
-                                     Child.new(name: "p1c3", position: 3)])
-    @parent1.save!
+    @model1 = model_class.new(name: "p1",
+                          children: [child_model_class.new(name: "p1c1", position: 1),
+                                     child_model_class.new(name: "p1c2", position: 2),
+                                     child_model_class.new(name: "p1c3", position: 3)])
+    @model1.save!
 
-    @parent2 = Parent.new(name: "p2",
-                          children: [Child.new(name: "p2c1").tap { |c| c.position = 1 },
-                                     Child.new(name: "p2c2").tap { |c| c.position = 2 }])
+    @model2 = model_class.new(name: "p2",
+                          children: [child_model_class.new(name: "p2c1").tap { |c| c.position = 1 },
+                                     child_model_class.new(name: "p2c2").tap { |c| c.position = 2 }])
 
-    @parent2.save!
+    @model2.save!
 
     enable_logging!
   end
 
   def test_load_associated
-    parentview = ParentView.new(@parent1)
+    parentview = viewmodel_class.new(@model1)
 
     childviews = parentview.load_associated(:children)
     assert_equal(3, childviews.size)
@@ -79,14 +40,14 @@ def test_load_associated
   end
 
   def test_serialize_view
-    view, _refs = serialize_with_references(ParentView.new(@parent1))
+    view, _refs = serialize_with_references(viewmodel_class.new(@model1))
 
 
-    assert_equal({ "_type"    => "Parent",
+    assert_equal({ "_type"    => "Model",
                    "_version" => 1,
-                   "id"       => @parent1.id,
-                   "name"     => @parent1.name,
-                   "children" => @parent1.children.map { |child| { "_type"    => "Child",
+                   "id"       => @model1.id,
+                   "name"     => @model1.name,
+                   "children" => @model1.children.map { |child| { "_type"    => "Child",
                                                                    "_version" => 1,
                                                                    "id"       => child.id,
                                                                    "name"     => child.name } } },
@@ -95,21 +56,21 @@ def test_serialize_view
 
   def test_loading_batching
     log_queries do
-      serialize(ParentView.load)
+      serialize(viewmodel_class.load)
     end
-    assert_equal(['Parent Load', 'Child Load'],
+    assert_equal(['Model Load', 'Child Load'],
                  logged_load_queries)
   end
 
   def test_create_from_view
     view = {
-      "_type"    => "Parent",
+      "_type"    => "Model",
       "name"     => "p",
       "children" => [{ "_type" => "Child", "name" => "c1" },
                      { "_type" => "Child", "name" => "c2" }]
     }
 
-    pv = ParentView.deserialize_from_view(view)
+    pv = viewmodel_class.deserialize_from_view(view)
     p = pv.model
 
     assert(!p.changed?)
@@ -126,33 +87,33 @@ def test_create_from_view
   end
 
   def test_editability_raises
-    no_edit_context = ParentView.new_deserialize_context(can_edit: false)
+    no_edit_context = viewmodel_class.new_deserialize_context(can_edit: false)
 
     assert_raises(ViewModel::AccessControlError) do
       # append child
-      ParentView.new(@parent1).append_associated(:children, { "_type" => "Child", "name" => "hi" }, deserialize_context: no_edit_context)
+      viewmodel_class.new(@model1).append_associated(:children, { "_type" => "Child", "name" => "hi" }, deserialize_context: no_edit_context)
     end
 
     assert_raises(ViewModel::AccessControlError) do
       # destroy child
-      ParentView.new(@parent1).delete_associated(:children, @parent1.children.first.id, deserialize_context: no_edit_context)
+      viewmodel_class.new(@model1).delete_associated(:children, @model1.children.first.id, deserialize_context: no_edit_context)
     end
   end
 
   def test_create_has_many_empty
-    view = { '_type' => 'Parent', 'name' => 'p', 'children' => [] }
-    pv = ParentView.deserialize_from_view(view)
+    view = { '_type' => 'Model', 'name' => 'p', 'children' => [] }
+    pv = viewmodel_class.deserialize_from_view(view)
     assert(pv.model.children.blank?)
   end
 
   def test_create_has_many
-    view = { '_type'    => 'Parent',
+    view = { '_type'    => 'Model',
              'name'     => 'p',
              'children' => [{ '_type' => 'Child', 'name' => 'c1' },
                             { '_type' => 'Child', 'name' => 'c2' }] }
 
-    context = ParentView.new_deserialize_context
-    pv = ParentView.deserialize_from_view(view, deserialize_context: context)
+    context = viewmodel_class.new_deserialize_context
+    pv = viewmodel_class.deserialize_from_view(view, deserialize_context: context)
 
     assert_contains_exactly(
       [pv.to_reference, pv.children[0].to_reference, pv.children[1].to_reference],
@@ -163,11 +124,11 @@ def test_create_has_many
 
   def test_nil_multiple_association
     view = {
-      "_type" => "Parent",
+      "_type" => "Model",
       "children" => nil
     }
     ex = assert_raises(ViewModel::DeserializationError::InvalidSyntax) do
-      ParentView.deserialize_from_view(view)
+      viewmodel_class.deserialize_from_view(view)
     end
 
     assert_match(/Invalid collection update value 'nil'/, ex.message)
@@ -175,39 +136,39 @@ def test_nil_multiple_association
 
   def test_non_array_multiple_association
     view = {
-      "_type" => "Parent",
+      "_type" => "Model",
       "children" => { '_type' => 'Child', 'name' => 'c1' }
     }
     ex = assert_raises(ViewModel::DeserializationError::InvalidSyntax) do
-      ParentView.deserialize_from_view(view)
+      viewmodel_class.deserialize_from_view(view)
     end
 
     assert_match(/Errors parsing collection functional update/, ex.message)
   end
 
   def test_replace_has_many
-    old_children = @parent1.children
+    old_children = @model1.children
 
-    alter_by_view!(ParentView, @parent1) do |view, refs|
+    alter_by_view!(viewmodel_class, @model1) do |view, refs|
       view['children'] = [{ '_type' => 'Child', 'name' => 'new_child' }]
     end
 
-    assert_equal(['new_child'], @parent1.children.map(&:name))
-    assert_equal([], Child.where(id: old_children.map(&:id)))
+    assert_equal(['new_child'], @model1.children.map(&:name))
+    assert_equal([], child_model_class.where(id: old_children.map(&:id)))
   end
 
   def test_replace_associated_has_many
-    old_children = @parent1.children
+    old_children = @model1.children
 
-    pv = ParentView.new(@parent1)
-    context = ParentView.new_deserialize_context
+    pv = viewmodel_class.new(@model1)
+    context = viewmodel_class.new_deserialize_context
 
     nc = pv.replace_associated(:children,
                                [{ '_type' => 'Child', 'name' => 'new_child' }],
                                deserialize_context: context)
 
     expected_edit_checks = [pv.to_reference,
-                            *old_children.map { |x| ViewModel::Reference.new(ChildView, x.id) },
+                            *old_children.map { |x| ViewModel::Reference.new(child_viewmodel_class, x.id) },
                             *nc.map(&:to_reference)]
 
     assert_contains_exactly(expected_edit_checks,
@@ -216,16 +177,16 @@ def test_replace_associated_has_many
     assert_equal(1, nc.size)
     assert_equal('new_child', nc[0].name)
 
-    @parent1.reload
-    assert_equal(['new_child'], @parent1.children.map(&:name))
-    assert_equal([], Child.where(id: old_children.map(&:id)))
+    @model1.reload
+    assert_equal(['new_child'], @model1.children.map(&:name))
+    assert_equal([], child_model_class.where(id: old_children.map(&:id)))
   end
 
   def test_replace_associated_has_many_functional
-    old_children = @parent1.children
+    old_children = @model1.children
 
-    pv = ParentView.new(@parent1)
-    context = ParentView.new_deserialize_context
+    pv = viewmodel_class.new(@model1)
+    context = viewmodel_class.new_deserialize_context
 
     update = build_fupdate do
       append([{ '_type' => 'Child', 'name' => 'new_child' }])
@@ -237,9 +198,9 @@ def test_replace_associated_has_many_functional
     new_child = nc.detect { |c| c.name == 'new_child' }
 
     expected_edit_checks = [pv.to_reference,
-                            ViewModel::Reference.new(ChildView, new_child.id),
-                            ViewModel::Reference.new(ChildView, old_children.first.id),
-                            ViewModel::Reference.new(ChildView, old_children.last.id)]
+                            ViewModel::Reference.new(child_viewmodel_class, new_child.id),
+                            ViewModel::Reference.new(child_viewmodel_class, old_children.first.id),
+                            ViewModel::Reference.new(child_viewmodel_class, old_children.last.id)]
 
     assert_contains_exactly(expected_edit_checks,
                             context.valid_edit_refs)
@@ -247,187 +208,187 @@ def test_replace_associated_has_many_functional
     assert_equal(3, nc.size)
     assert_equal('renamed p1c1', nc[0].name)
 
-    @parent1.reload
-    assert_equal(['renamed p1c1', 'p1c2', 'new_child'], @parent1.children.order(:position).map(&:name))
-    assert_equal([], Child.where(id: old_children.last.id))
+    @model1.reload
+    assert_equal(['renamed p1c1', 'p1c2', 'new_child'], @model1.children.order(:position).map(&:name))
+    assert_equal([], child_model_class.where(id: old_children.last.id))
   end
 
   def test_remove_has_many
-    old_children = @parent1.children
-    _, context = alter_by_view!(ParentView, @parent1) do |view, refs|
+    old_children = @model1.children
+    _, context = alter_by_view!(viewmodel_class, @model1) do |view, refs|
       view['children'] = []
     end
 
-    expected_edit_checks = [ViewModel::Reference.new(ParentView, @parent1.id)] +
-                           old_children.map { |x| ViewModel::Reference.new(ChildView, x.id) }
+    expected_edit_checks = [ViewModel::Reference.new(viewmodel_class, @model1.id)] +
+                           old_children.map { |x| ViewModel::Reference.new(child_viewmodel_class, x.id) }
 
     assert_equal(Set.new(expected_edit_checks),
                  context.valid_edit_refs.to_set)
 
-    assert_equal([], @parent1.children, 'no children associated with parent1')
-    assert(Child.where(id: old_children.map(&:id)).blank?, 'all children deleted')
+    assert_equal([], @model1.children, 'no children associated with parent1')
+    assert(child_model_class.where(id: old_children.map(&:id)).blank?, 'all children deleted')
   end
 
   def test_delete_associated_has_many
-    c1, c2, c3 = @parent1.children.order(:position).to_a
+    c1, c2, c3 = @model1.children.order(:position).to_a
 
-    pv = ParentView.new(@parent1)
-    context = ParentView.new_deserialize_context
+    pv = viewmodel_class.new(@model1)
+    context = viewmodel_class.new_deserialize_context
 
     pv.delete_associated(:children, c1.id,
                          deserialize_context: context)
 
-    expected_edit_checks = [ViewModel::Reference.new(ParentView, @parent1.id),
-                            ViewModel::Reference.new(ChildView,  c1.id)].to_set
+    expected_edit_checks = [ViewModel::Reference.new(viewmodel_class, @model1.id),
+                            ViewModel::Reference.new(child_viewmodel_class,  c1.id)].to_set
 
     assert_equal(expected_edit_checks,
                  context.valid_edit_refs.to_set)
 
-    @parent1.reload
-    assert_equal([c2, c3], @parent1.children.order(:position))
-    assert(Child.where(id: c1.id).blank?, 'old child deleted')
+    @model1.reload
+    assert_equal([c2, c3], @model1.children.order(:position))
+    assert(child_model_class.where(id: c1.id).blank?, 'old child deleted')
   end
 
   def test_edit_has_many
-    c1, c2, c3 = @parent1.children.order(:position).to_a
+    c1, c2, c3 = @model1.children.order(:position).to_a
 
-    pv, context = alter_by_view!(ParentView, @parent1) do |view, _refs|
+    pv, context = alter_by_view!(viewmodel_class, @model1) do |view, _refs|
       view['children'].shift
       view['children'] << { '_type' => 'Child', 'name' => 'new_c' }
     end
     nc = pv.children.detect { |c| c.name == 'new_c' }
 
     assert_contains_exactly(
-      [ViewModel::Reference.new(ParentView, @parent1.id),
-       ViewModel::Reference.new(ChildView,  c1.id),  # deleted child
-       ViewModel::Reference.new(ChildView,  nc.id)], # created child
+      [ViewModel::Reference.new(viewmodel_class, @model1.id),
+       ViewModel::Reference.new(child_viewmodel_class,  c1.id),  # deleted child
+       ViewModel::Reference.new(child_viewmodel_class,  nc.id)], # created child
       context.valid_edit_refs)
 
-    assert_equal([c2, c3, Child.find_by_name('new_c')],
-                 @parent1.children.order(:position))
-    assert(Child.where(id: c1.id).blank?)
+    assert_equal([c2, c3, child_model_class.find_by_name('new_c')],
+                 @model1.children.order(:position))
+    assert(child_model_class.where(id: c1.id).blank?)
   end
 
   def test_append_associated_move_has_many
-    c1, c2, c3 = @parent1.children.order(:position).to_a
-    pv = ParentView.new(@parent1)
+    c1, c2, c3 = @model1.children.order(:position).to_a
+    pv = viewmodel_class.new(@model1)
 
     # insert before
     pv.append_associated(:children,
                          { '_type' => 'Child', 'id' => c3.id },
-                         before: ViewModel::Reference.new(ChildView, c1.id),
-                         deserialize_context: (context = ParentView.new_deserialize_context))
+                         before: ViewModel::Reference.new(child_viewmodel_class, c1.id),
+                         deserialize_context: (context = viewmodel_class.new_deserialize_context))
 
     expected_edit_checks = [pv.to_reference]
     assert_contains_exactly(expected_edit_checks, context.valid_edit_refs)
 
     assert_equal([c3, c1, c2],
-                 @parent1.children.order(:position))
+                 @model1.children.order(:position))
 
     # insert after
     pv.append_associated(:children,
                          { '_type' => 'Child', 'id' => c3.id },
-                         after: ViewModel::Reference.new(ChildView, c1.id),
-                         deserialize_context: (context = ParentView.new_deserialize_context))
+                         after: ViewModel::Reference.new(child_viewmodel_class, c1.id),
+                         deserialize_context: (context = viewmodel_class.new_deserialize_context))
 
     assert_contains_exactly(expected_edit_checks, context.valid_edit_refs)
 
     assert_equal([c1, c3, c2],
-                 @parent1.children.order(:position))
+                 @model1.children.order(:position))
 
     # append
     pv.append_associated(:children,
                          { '_type' => 'Child', 'id' => c3.id },
-                         deserialize_context: (context = ParentView.new_deserialize_context))
+                         deserialize_context: (context = viewmodel_class.new_deserialize_context))
 
     assert_contains_exactly(expected_edit_checks, context.valid_edit_refs)
 
     assert_equal([c1, c2, c3],
-                 @parent1.children.order(:position))
+                 @model1.children.order(:position))
 
     # move from another parent
-    p2c1 = @parent2.children.order(:position).first
+    p2c1 = @model2.children.order(:position).first
 
     pv.append_associated(:children,
                          { '_type' => 'Child', 'id' => p2c1.id },
-                         deserialize_context: (context = ParentView.new_deserialize_context))
+                         deserialize_context: (context = viewmodel_class.new_deserialize_context))
 
-    expected_edit_checks = [ViewModel::Reference.new(ParentView, @parent1.id),
-                            ViewModel::Reference.new(ParentView, @parent2.id)]
+    expected_edit_checks = [ViewModel::Reference.new(viewmodel_class, @model1.id),
+                            ViewModel::Reference.new(viewmodel_class, @model2.id)]
 
     assert_contains_exactly(expected_edit_checks, context.valid_edit_refs)
 
     assert_equal([c1, c2, c3, p2c1],
-                 @parent1.children.order(:position))
+                 @model1.children.order(:position))
   end
 
   def test_append_associated_insert_has_many
-    c1, c2, c3 = @parent1.children.order(:position).to_a
-    pv = ParentView.new(@parent1)
+    c1, c2, c3 = @model1.children.order(:position).to_a
+    pv = viewmodel_class.new(@model1)
 
     # insert before
     pv.append_associated(:children,
                          { '_type' => 'Child', 'name' => 'new1' },
-                         before: ViewModel::Reference.new(ChildView, c2.id),
-                         deserialize_context: (context = ParentView.new_deserialize_context))
+                         before: ViewModel::Reference.new(child_viewmodel_class, c2.id),
+                         deserialize_context: (context = viewmodel_class.new_deserialize_context))
 
-    n1 = Child.find_by_name('new1')
+    n1 = child_model_class.find_by_name('new1')
 
-    expected_edit_checks = [ViewModel::Reference.new(ParentView, @parent1.id),
-                            ViewModel::Reference.new(ChildView, n1.id)]
+    expected_edit_checks = [ViewModel::Reference.new(viewmodel_class, @model1.id),
+                            ViewModel::Reference.new(child_viewmodel_class, n1.id)]
 
     assert_contains_exactly(expected_edit_checks, context.valid_edit_refs)
 
     assert_equal([c1, n1, c2, c3],
-                 @parent1.children.order(:position))
+                 @model1.children.order(:position))
 
     # insert after
     pv.append_associated(:children,
                          { '_type' => 'Child', 'name' => 'new2' },
-                         after: ViewModel::Reference.new(ChildView, c2.id),
-                         deserialize_context: (context = ParentView.new_deserialize_context))
+                         after: ViewModel::Reference.new(child_viewmodel_class, c2.id),
+                         deserialize_context: (context = viewmodel_class.new_deserialize_context))
 
-    n2 = Child.find_by_name('new2')
+    n2 = child_model_class.find_by_name('new2')
 
-    expected_edit_checks = [ViewModel::Reference.new(ParentView, @parent1.id),
-                            ViewModel::Reference.new(ChildView, n2.id)]
+    expected_edit_checks = [ViewModel::Reference.new(viewmodel_class, @model1.id),
+                            ViewModel::Reference.new(child_viewmodel_class, n2.id)]
 
     assert_contains_exactly(expected_edit_checks, context.valid_edit_refs)
 
     assert_equal([c1, n1, c2, n2, c3],
-                 @parent1.children.order(:position))
+                 @model1.children.order(:position))
 
     # append
     pv.append_associated(:children,
                          { '_type' => 'Child', 'name' => 'new3' },
-                         deserialize_context: (context = ParentView.new_deserialize_context))
+                         deserialize_context: (context = viewmodel_class.new_deserialize_context))
 
-    n3 = Child.find_by_name('new3')
+    n3 = child_model_class.find_by_name('new3')
 
-    expected_edit_checks = [ViewModel::Reference.new(ParentView, @parent1.id),
-                            ViewModel::Reference.new(ChildView, n3.id)]
+    expected_edit_checks = [ViewModel::Reference.new(viewmodel_class, @model1.id),
+                            ViewModel::Reference.new(child_viewmodel_class, n3.id)]
 
     assert_contains_exactly(expected_edit_checks, context.valid_edit_refs)
 
     assert_equal([c1, n1, c2, n2, c3, n3],
-                 @parent1.children.order(:position))
+                 @model1.children.order(:position))
   end
 
   def test_edit_implicit_list_position
-    c1, c2, c3 = @parent1.children.order(:position).to_a
+    c1, c2, c3 = @model1.children.order(:position).to_a
 
-    alter_by_view!(ParentView, @parent1) do |view, refs|
+    alter_by_view!(viewmodel_class, @model1) do |view, refs|
       view['children'].reverse!
       view['children'].insert(1, { '_type' => 'Child', 'name' => 'new_c' })
     end
 
-    assert_equal([c3, Child.find_by_name('new_c'), c2, c1],
-                 @parent1.children.order(:position))
+    assert_equal([c3, child_model_class.find_by_name('new_c'), c2, c1],
+                 @model1.children.order(:position))
   end
 
   def test_edit_missing_child
     view = {
-      "_type" => "Parent",
+      "_type" => "Model",
       "children" => [{
                        "_type" => "Child",
                        "id"    => 9999
@@ -435,37 +396,37 @@ def test_edit_missing_child
     }
 
     ex = assert_raises(ViewModel::DeserializationError::NotFound) do
-      ParentView.deserialize_from_view(view)
+      viewmodel_class.deserialize_from_view(view)
     end
 
-    assert_equal(ex.nodes, [ViewModel::Reference.new(ChildView, 9999)])
+    assert_equal(ex.nodes, [ViewModel::Reference.new(child_viewmodel_class, 9999)])
   end
 
   def test_move_child_to_new
-    old_children = @parent1.children.order(:position)
+    old_children = @model1.children.order(:position)
     moved_child = old_children[1]
 
-    moved_child_ref = update_hash_for(ChildView, moved_child)
+    moved_child_ref = update_hash_for(child_viewmodel_class, moved_child)
 
-    view = { '_type'    => 'Parent',
+    view = { '_type'    => 'Model',
              'name'     => 'new_p',
              'children' => [moved_child_ref,
                             { '_type' => 'Child', 'name' => 'new' }] }
 
     retained_children = old_children - [moved_child]
-    release_view = { '_type'    => 'Parent',
-                     'id'       => @parent1.id,
-                     'children' => retained_children.map { |c| update_hash_for(ChildView, c) } }
+    release_view = { '_type'    => 'Model',
+                     'id'       => @model1.id,
+                     'children' => retained_children.map { |c| update_hash_for(child_viewmodel_class, c) } }
 
-    pv = ParentView.deserialize_from_view([view, release_view])
+    pv = viewmodel_class.deserialize_from_view([view, release_view])
 
     new_parent = pv.first.model
     new_parent.reload
 
     # child should be removed from old parent
-    @parent1.reload
+    @model1.reload
     assert_equal(retained_children,
-                 @parent1.children.order(:position))
+                 @model1.children.order(:position))
 
     # child should be added to new parent
     new_children = new_parent.children.order(:position)
@@ -474,18 +435,18 @@ def test_move_child_to_new
   end
 
   def test_has_many_cannot_take_from_outside_tree
-    old_children = @parent1.children.order(:position)
+    old_children = @model1.children.order(:position)
 
     assert_raises(ViewModel::DeserializationError::ParentNotFound) do
-      alter_by_view!(ParentView, @parent2) do |p2, _refs|
-        p2['children'] = old_children.map { |x| update_hash_for(ChildView, x) }
+      alter_by_view!(viewmodel_class, @model2) do |p2, _refs|
+        p2['children'] = old_children.map { |x| update_hash_for(child_viewmodel_class, x) }
       end
     end
   end
 
   def test_has_many_cannot_duplicate_unreleased_children
     assert_raises(ViewModel::DeserializationError::DuplicateNodes) do
-      alter_by_view!(ParentView, [@parent1, @parent2]) do |(p1, p2), _refs|
+      alter_by_view!(viewmodel_class, [@model1, @model2]) do |(p1, p2), _refs|
         p2['children'] = p1['children'].deep_dup
       end
     end
@@ -493,7 +454,7 @@ def test_has_many_cannot_duplicate_unreleased_children
 
   def test_has_many_cannot_duplicate_implicitly_unreleased_children
     assert_raises(ViewModel::DeserializationError::ParentNotFound) do
-      alter_by_view!(ParentView, [@parent1, @parent2]) do |(p1, p2), _refs|
+      alter_by_view!(viewmodel_class, [@model1, @model2]) do |(p1, p2), _refs|
         p2['children'] = p1['children']
         p1.delete('children')
       end
@@ -501,74 +462,73 @@ def test_has_many_cannot_duplicate_implicitly_unreleased_children
   end
 
   def test_move_child_to_existing
-    old_children = @parent1.children.order(:position)
+    old_children = @model1.children.order(:position)
     moved_child = old_children[1]
 
-    view = ParentView.new(@parent2).to_hash
-    view['children'] << ChildView.new(moved_child).to_hash
+    view = viewmodel_class.new(@model2).to_hash
+    view['children'] << child_viewmodel_class.new(moved_child).to_hash
 
     retained_children = old_children - [moved_child]
-    release_view = { '_type' => 'Parent', 'id' => @parent1.id,
-                     'children' => retained_children.map { |c| update_hash_for(ChildView, c) }}
+    release_view = { '_type' => 'Model', 'id' => @model1.id,
+                     'children' => retained_children.map { |c| update_hash_for(child_viewmodel_class, c) }}
 
-    ParentView.deserialize_from_view([view, release_view])
+    viewmodel_class.deserialize_from_view([view, release_view])
 
-    @parent1.reload
-    @parent2.reload
+    @model1.reload
+    @model2.reload
 
     # child should be removed from old parent and positions updated
-    assert_equal(retained_children, @parent1.children.order(:position))
+    assert_equal(retained_children, @model1.children.order(:position))
 
     # child should be added to new parent with valid position
-    new_children = @parent2.children.order(:position)
+    new_children = @model2.children.order(:position)
     assert_equal(%w(p2c1 p2c2 p1c2), new_children.map(&:name))
     assert_equal(moved_child, new_children.last)
   end
 
   def test_has_many_append_child
-    ParentView.new(@parent1).append_associated(:children, { "_type" => "Child", "name" => "new" })
+    viewmodel_class.new(@model1).append_associated(:children, { "_type" => "Child", "name" => "new" })
 
-    @parent1.reload
+    @model1.reload
 
-    assert_equal(4, @parent1.children.size)
-    lc = @parent1.children.order(:position).last
+    assert_equal(4, @model1.children.size)
+    lc = @model1.children.order(:position).last
     assert_equal("new", lc.name)
   end
 
   def test_has_many_append_and_update_existing_association
-    child = @parent1.children[1]
+    child = @model1.children[1]
 
-    cv = ChildView.new(child).to_hash
+    cv = child_viewmodel_class.new(child).to_hash
     cv["name"] = "newname"
 
-    ParentView.new(@parent1).append_associated(:children, cv)
+    viewmodel_class.new(@model1).append_associated(:children, cv)
 
-    @parent1.reload
+    @model1.reload
 
     # Child should have been moved to the end (and edited)
-    assert_equal(3, @parent1.children.size)
-    c1, c2, c3 = @parent1.children.order(:position)
+    assert_equal(3, @model1.children.size)
+    c1, c2, c3 = @model1.children.order(:position)
     assert_equal("p1c1", c1.name)
     assert_equal("p1c3", c2.name)
     assert_equal(child, c3)
     assert_equal("newname", c3.name)
-
   end
 
   def test_has_many_move_existing_association
-    p1c2 = @parent1.children[1]
+    p1c2 = @model1.children[1]
     assert_equal(2, p1c2.position)
 
-    ParentView.new(@parent2).append_associated("children", { "_type" => "Child", "id" => p1c2.id })
+    viewmodel_class.new(@model2).append_associated("children", { "_type" => "Child", "id" => p1c2.id })
 
-    @parent1.reload
-    @parent2.reload
+    @model1.reload
+    @model2.reload
 
-    p1c = @parent1.children.order(:position)
+    p1c = @model1.children.order(:position)
     assert_equal(2, p1c.size)
     assert_equal(["p1c1", "p1c3"], p1c.map(&:name))
 
-    p2c = @parent2.children.order(:position)
+    p2c = @model2.children.order(:position)
     assert_equal(3, p2c.size)
     assert_equal(["p2c1", "p2c2", "p1c2"], p2c.map(&:name))
     assert_equal(p1c2, p2c[2])
@@ -576,44 +536,44 @@ def test_has_many_move_existing_association
   end
 
   def test_has_many_remove_existing_association
-    child = @parent1.children[1]
+    child = @model1.children[1]
 
-    ParentView.new(@parent1).delete_associated(:children, child.id)
+    viewmodel_class.new(@model1).delete_associated(:children, child.id)
 
-    @parent1.reload
+    @model1.reload
 
     # Child should have been removed
-    assert_equal(2, @parent1.children.size)
-    c1, c2 = @parent1.children.order(:position)
+    assert_equal(2, @model1.children.size)
+    c1, c2 = @model1.children.order(:position)
     assert_equal("p1c1", c1.name)
     assert_equal("p1c3", c2.name)
 
-    assert_equal(0, Child.where(id: child.id).size)
+    assert_equal(0, child_model_class.where(id: child.id).size)
   end
 
   def test_move_and_edit_child_to_new
-    child = @parent1.children[1]
+    child = @model1.children[1]
 
-    child_view = ChildView.new(child).to_hash
+    child_view = child_viewmodel_class.new(child).to_hash
     child_view["name"] = "changed"
 
-    view = { "_type" => "Parent",
+    view = { "_type" => "Model",
              "name" => "new_p",
              "children" => [child_view, { "_type" => "Child", "name" => "new" }]}
 
     # TODO this is as awkward here as it is in the application
-    release_view = { "_type" => "Parent",
-                     "id" => @parent1.id,
-                     "children" => [{ "_type" => "Child", "id" => @parent1.children[0].id },
-                                    { "_type" => "Child", "id" => @parent1.children[2].id }]}
+    release_view = { "_type" => "Model",
+                     "id" => @model1.id,
+                     "children" => [{ "_type" => "Child", "id" => @model1.children[0].id },
+                                    { "_type" => "Child", "id" => @model1.children[2].id }]}
 
-    pv = ParentView.deserialize_from_view([view, release_view])
+    pv = viewmodel_class.deserialize_from_view([view, release_view])
     new_parent = pv.first.model
 
     # child should be removed from old parent and positions updated
-    @parent1.reload
-    assert_equal(2, @parent1.children.size, "database has 2 children")
-    oc1, oc2 = @parent1.children.order(:position)
+    @model1.reload
+    assert_equal(2, @model1.children.size, "database has 2 children")
+    oc1, oc2 = @model1.children.order(:position)
     assert_equal("p1c1", oc1.name, "database c1 unchanged")
     assert_equal("p1c3", oc2.name, "database c2 unchanged")
 
@@ -626,32 +586,32 @@ def test_move_and_edit_child_to_new
   end
 
   def test_move_and_edit_child_to_existing
-    old_child = @parent1.children[1]
+    old_child = @model1.children[1]
 
-    old_child_view = ChildView.new(old_child).to_hash
+    old_child_view = child_viewmodel_class.new(old_child).to_hash
     old_child_view["name"] = "changed"
-    view = ParentView.new(@parent2).to_hash
+    view = viewmodel_class.new(@model2).to_hash
     view["children"] << old_child_view
 
-    release_view = {"_type" => "Parent", "id" => @parent1.id,
-                    "children" => [{"_type" => "Child", "id" => @parent1.children[0].id},
-                                   {"_type" => "Child", "id" => @parent1.children[2].id}]}
+    release_view = {"_type" => "Model", "id" => @model1.id,
+                    "children" => [{"_type" => "Child", "id" => @model1.children[0].id},
+                                   {"_type" => "Child", "id" => @model1.children[2].id}]}
 
-    ParentView.deserialize_from_view([view, release_view])
+    viewmodel_class.deserialize_from_view([view, release_view])
 
-    @parent1.reload
-    @parent2.reload
+    @model1.reload
+    @model2.reload
 
     # child should be removed from old parent and positions updated
-    assert_equal(2, @parent1.children.size)
-    oc1, oc2 = @parent1.children.order(:position)
+    assert_equal(2, @model1.children.size)
+    oc1, oc2 = @model1.children.order(:position)
 
     assert_equal("p1c1", oc1.name)
     assert_equal("p1c3", oc2.name)
 
     # child should be added to new parent with valid position
-    assert_equal(3, @parent2.children.size)
-    nc1, _, nc3 = @parent2.children.order(:position)
+    assert_equal(3, @model2.children.size)
+    nc1, _, nc3 = @model2.children.order(:position)
     assert_equal("p2c1", nc1.name)
 
     assert_equal("p2c1", nc1.name)
@@ -661,27 +621,27 @@ def test_move_and_edit_child_to_existing
   end
 
   def test_functional_update_append
-    children_before = @parent1.children.order(:position).pluck(:id)
+    children_before = @model1.children.order(:position).pluck(:id)
     fupdate = build_fupdate do
       append([{ '_type' => 'Child' },
               { '_type' => 'Child' }])
     end
 
-    append_view     = { '_type'    => 'Parent',
-                        'id'       => @parent1.id,
+    append_view     = { '_type'    => 'Model',
+                        'id'       => @model1.id,
                         'children' => fupdate }
 
-    result          = ParentView.deserialize_from_view(append_view)
-    @parent1.reload
+    result          = viewmodel_class.deserialize_from_view(append_view)
+    @model1.reload
 
     created_children = result.children[-2,2].map(&:id)
 
     assert_equal(children_before + created_children,
-                 @parent1.children.order(:position).pluck(:id))
+                 @model1.children.order(:position).pluck(:id))
   end
 
   def test_functional_update_append_before_mid
-    c1, c2, c3  = @parent1.children.order(:position)
+    c1, c2, c3  = @model1.children.order(:position)
 
     fupdate = build_fupdate do
       append([{ '_type' => 'Child', 'name' => 'new c1' },
@@ -689,36 +649,36 @@ def test_functional_update_append_before_mid
              before: { '_type' => 'Child', 'id' => c2.id })
     end
 
-    append_view = { '_type'    => 'Parent',
-                    'id'       => @parent1.id,
+    append_view = { '_type'    => 'Model',
+                    'id'       => @model1.id,
                     'children' => fupdate }
-    ParentView.deserialize_from_view(append_view)
-    @parent1.reload
+    viewmodel_class.deserialize_from_view(append_view)
+    @model1.reload
 
     assert_equal([c1.name, 'new c1', 'new c2', c2.name, c3.name],
-                 @parent1.children.order(:position).pluck(:name))
+                 @model1.children.order(:position).pluck(:name))
   end
 
   def test_functional_update_append_before_reorder
-    c1, c2, c3  = @parent1.children.order(:position)
+    c1, c2, c3  = @model1.children.order(:position)
 
     fupdate = build_fupdate do
       append([{ '_type' => 'Child', 'id' => c3.id }],
              before: { '_type' => 'Child', 'id' => c2.id })
     end
 
-    append_view = { '_type'    => 'Parent',
-                    'id'       => @parent1.id,
+    append_view = { '_type'    => 'Model',
+                    'id'       => @model1.id,
                     'children' => fupdate }
-    ParentView.deserialize_from_view(append_view)
-    @parent1.reload
+    viewmodel_class.deserialize_from_view(append_view)
+    @model1.reload
 
     assert_equal([c1.name, c3.name, c2.name],
-                 @parent1.children.order(:position).pluck(:name))
+                 @model1.children.order(:position).pluck(:name))
   end
 
   def test_functional_update_append_before_beginning
-    c1, c2, c3  = @parent1.children.order(:position)
+    c1, c2, c3  = @model1.children.order(:position)
 
     fupdate = build_fupdate do
       append([{ '_type' => 'Child', 'name' => 'new c1' },
@@ -726,18 +686,18 @@ def test_functional_update_append_before_beginning
              before: { '_type' => 'Child', 'id' => c1.id })
     end
 
-    append_view = { '_type'    => 'Parent',
-                    'id'       => @parent1.id,
+    append_view = { '_type'    => 'Model',
+                    'id'       => @model1.id,
                     'children' => fupdate }
-    ParentView.deserialize_from_view(append_view)
-    @parent1.reload
+    viewmodel_class.deserialize_from_view(append_view)
+    @model1.reload
 
     assert_equal(['new c1', 'new c2', c1.name, c2.name, c3.name],
-                 @parent1.children.order(:position).pluck(:name))
+                 @model1.children.order(:position).pluck(:name))
   end
 
   def test_functional_update_append_before_corpse
-    _, c2, _ = @parent1.children.order(:position)
+    _, c2, _ = @model1.children.order(:position)
     c2.destroy
 
     fupdate = build_fupdate do
@@ -746,16 +706,16 @@ def test_functional_update_append_before_corpse
              before: { '_type' => 'Child', 'id' => c2.id })
     end
 
-    append_view = { '_type'    => 'Parent',
-                    'id'       => @parent1.id,
+    append_view = { '_type'    => 'Model',
+                    'id'       => @model1.id,
                     'children' => fupdate }
     assert_raises(ViewModel::DeserializationError::AssociatedNotFound) do
-      ParentView.deserialize_from_view(append_view)
+      viewmodel_class.deserialize_from_view(append_view)
     end
   end
 
   def test_functional_update_append_after_mid
-    c1, c2, c3  = @parent1.children.order(:position)
+    c1, c2, c3  = @model1.children.order(:position)
 
     fupdate = build_fupdate do
       append([{ '_type' => 'Child', 'name' => 'new c1' },
@@ -763,18 +723,18 @@ def test_functional_update_append_after_mid
              after: { '_type' => 'Child', 'id' => c2.id })
     end
 
-    append_view = { '_type'    => 'Parent',
-                    'id'       => @parent1.id,
+    append_view = { '_type'    => 'Model',
+                    'id'       => @model1.id,
                     'children' => fupdate }
-    ParentView.deserialize_from_view(append_view)
-    @parent1.reload
+    viewmodel_class.deserialize_from_view(append_view)
+    @model1.reload
 
     assert_equal([c1.name, c2.name, 'new c1', 'new c2', c3.name],
-                 @parent1.children.order(:position).pluck(:name))
+                 @model1.children.order(:position).pluck(:name))
   end
 
   def test_functional_update_append_after_end
-    c1, c2, c3  = @parent1.children.order(:position)
+    c1, c2, c3  = @model1.children.order(:position)
 
     fupdate = build_fupdate do
       append([{ '_type' => 'Child', 'name' => 'new c1' },
@@ -782,18 +742,18 @@ def test_functional_update_append_after_end
              after: { '_type' => 'Child', 'id' => c3.id, })
     end
 
-    append_view = { '_type'    => 'Parent',
-                    'id'       => @parent1.id,
+    append_view = { '_type'    => 'Model',
+                    'id'       => @model1.id,
                     'children' => fupdate }
-    ParentView.deserialize_from_view(append_view)
-    @parent1.reload
+    viewmodel_class.deserialize_from_view(append_view)
+    @model1.reload
 
     assert_equal([c1.name, c2.name, c3.name, 'new c1', 'new c2'],
-                 @parent1.children.order(:position).pluck(:name))
+                 @model1.children.order(:position).pluck(:name))
   end
 
   def test_functional_update_append_after_corpse
-    _, c2, _ = @parent1.children.order(:position)
+    _, c2, _ = @model1.children.order(:position)
     c2.destroy
 
     fupdate = build_fupdate do
@@ -803,32 +763,32 @@ def test_functional_update_append_after_corpse
              )
     end
 
-    append_view = { '_type'    => 'Parent',
-                    'id'       => @parent1.id,
+    append_view = { '_type'    => 'Model',
+                    'id'       => @model1.id,
                     'children' => fupdate }
     assert_raises(ViewModel::DeserializationError::AssociatedNotFound) do
-      ParentView.deserialize_from_view(append_view)
+      viewmodel_class.deserialize_from_view(append_view)
     end
   end
 
   def test_functional_update_remove_success
-    c1_id, c2_id, c3_id = @parent1.children.pluck(:id)
+    c1_id, c2_id, c3_id = @model1.children.pluck(:id)
 
     fupdate = build_fupdate do
       remove([{ '_type' => 'Child', 'id' => c2_id }])
     end
 
-    remove_view         = { '_type'    => 'Parent',
-                            'id'       => @parent1.id,
+    remove_view         = { '_type'    => 'Model',
+                            'id'       => @model1.id,
                             'children' => fupdate }
-    ParentView.deserialize_from_view(remove_view)
-    @parent1.reload
+    viewmodel_class.deserialize_from_view(remove_view)
+    @model1.reload
 
-    assert_equal([c1_id, c3_id], @parent1.children.pluck(:id))
+    assert_equal([c1_id, c3_id], @model1.children.pluck(:id))
   end
 
   def test_functional_update_remove_failure
-    c_id        = @parent1.children.pluck(:id).first
+    c_id        = @model1.children.pluck(:id).first
 
     fupdate = build_fupdate do
       remove([{ '_type' => 'Child',
@@ -836,19 +796,19 @@ def test_functional_update_remove_failure
                 'name'  => 'remove and update disallowed' }])
     end
 
-    remove_view = { '_type'    => 'Parent',
-                    'id'       => @parent1.id,
+    remove_view = { '_type'    => 'Model',
+                    'id'       => @model1.id,
                     'children' => fupdate }
 
     ex = assert_raises(ViewModel::DeserializationError::InvalidSyntax) do
-      ParentView.deserialize_from_view(remove_view)
+      viewmodel_class.deserialize_from_view(remove_view)
     end
 
     assert_match(/Removed entities must have only _type and id fields/, ex.message)
   end
 
   def test_functional_update_update_success
-    c1_id, c2_id, c3_id = @parent1.children.pluck(:id)
+    c1_id, c2_id, c3_id = @model1.children.pluck(:id)
 
     fupdate = build_fupdate do
       update([{ '_type' => 'Child',
@@ -856,34 +816,36 @@ def test_functional_update_update_success
                 'name'  => 'Functionally Updated Child' }])
     end
 
-    update_view         = { '_type'    => 'Parent',
-                            'id'       => @parent1.id,
+    update_view         = { '_type'    => 'Model',
+                            'id'       => @model1.id,
                             'children' => fupdate }
-    ParentView.deserialize_from_view(update_view)
-    @parent1.reload
+    viewmodel_class.deserialize_from_view(update_view)
+    @model1.reload
 
-    assert_equal([c1_id, c2_id, c3_id], @parent1.children.pluck(:id))
-    assert_equal('Functionally Updated Child', Child.find(c2_id).name)
+    assert_equal([c1_id, c2_id, c3_id], @model1.children.pluck(:id))
+    assert_equal('Functionally Updated Child', child_model_class.find(c2_id).name)
   end
 
   def test_functional_update_update_failure
-    cnew                = Child.create(parent: Parent.create).id
+    cnew = child_model_class.create(model: model_class.create, position: 0).id
 
     fupdate = build_fupdate do
       update([{ '_type' => 'Child', 'id' => cnew }])
     end
 
-    update_view         = { '_type'    => 'Parent',
-                            'id'       => @parent1.id,
-                            'children' => fupdate }
+    update_view = {
+      '_type'    => 'Model',
+      'id'       => @model1.id,
+      'children' => fupdate,
+    }
 
     assert_raises(ViewModel::DeserializationError::AssociatedNotFound) do
-      ParentView.deserialize_from_view(update_view)
+      viewmodel_class.deserialize_from_view(update_view)
     end
   end
 
   def test_functional_update_duplicate_refs
-    child_id    = @parent1.children.pluck(:id).first
+    child_id = @model1.children.pluck(:id).first
 
     fupdate = build_fupdate do
       # remove and append the same child
@@ -891,67 +853,329 @@ def test_functional_update_duplicate_refs
       append([{ '_type' => 'Child', 'id' => child_id }])
     end
 
-    update_view = { '_type'    => 'Parent',
-                    'id'       => @parent1.id,
+    update_view = { '_type'    => 'Model',
+                    'id'       => @model1.id,
                     'children' => fupdate }
 
     ex = assert_raises(ViewModel::DeserializationError::InvalidStructure) do
-      ParentView.deserialize_from_view(update_view)
+      viewmodel_class.deserialize_from_view(update_view)
     end
 
     assert_match(/Duplicate functional update targets\b.*\bChild\b/, ex.message)
   end
 
+  describe 'owned reference children' do
+    def child_attributes
+      super.merge(viewmodel: ->(v) { root! })
+    end
+
+    def new_model
+      new_children = (1 .. 2).map { |n| child_model_class.new(name: "c#{n}", position: n) }
+      model_class.new(name: 'm1', children: new_children)
+    end
 
-  class RenamedTest < ActiveSupport::TestCase
-    include ARVMTestUtilities
+    it 'makes a reference association' do
+      assert(subject_association.referenced?)
+    end
 
-    def before_all
-      super
+    it 'makes an owned association' do
+      assert(subject_association.owned?)
+    end
+
+    it 'loads and batches' do
+      create_model!
 
-      build_viewmodel(:Parent) do
-        define_schema do |t|
-          t.string :name
+      log_queries do
+        serialize(ModelView.load)
+      end
+
+      assert_equal(['Model Load', 'Child Load'], logged_load_queries)
+    end
+
+    it 'serializes' do
+      model = create_model!
+      view, refs = serialize_with_references(ModelView.new(model))
+
+      children = model.children.sort_by(&:position)
+      assert_equal(children.size, view['children'].size)
+
+      child_refs = view['children'].map { |c| c['_ref'] }
+      child_views = child_refs.map { |r| refs[r] }
+
+      children.zip(child_views).each do |child, child_view|
+        assert_equal(child_view,
+                     { '_type'    => 'Child',
+                       '_version' => 1,
+                       'id'       => child.id,
+                       'name'     => child.name })
+      end
+
+      assert_equal({ '_type'    => 'Model',
+                     '_version' => 1,
+                     'id'       => model.id,
+                     'name'     => model.name,
+                     'children' => view['children'] },
+                   view)
+    end
+
+    it 'creates from view' do
+      view = {
+        '_type' => 'Model',
+        'name'  => 'p',
+        'children' => [{ '_ref' => 'r1' }],
+      }
+
+      refs = {
+        'r1' => { '_type' => 'Child', 'name' => 'newkid' },
+      }
+
+      pv = ModelView.deserialize_from_view(view, references: refs)
+      p = pv.model
+
+      assert(!p.changed?)
+      assert(!p.new_record?)
+
+      assert_equal('p', p.name)
+
+      assert(p.children.present?)
+      assert_equal('newkid', p.children[0].name)
+    end
+
+    it 'updates with adding a child' do
+      model = create_model!
+
+      alter_by_view!(ModelView, model) do |view, refs|
+        view['children'] << { '_ref' => 'ref1' }
+        refs['ref1'] = {
+          '_type' => 'Child',
+          'name' => 'newchildname',
+        }
+      end
+
+      assert_equal(3, model.children.size)
+      assert_equal('newchildname', model.children.last.name)
+    end
+
+    it 'updates with adding a child functionally' do
+      model = create_model!
+
+      alter_by_view!(ModelView, model) do |view, refs|
+        refs.clear
+
+        view['children'] = build_fupdate do
+          append([{ '_ref' => 'ref1' }])
         end
 
-        define_model do
-          has_many :children, dependent: :destroy, inverse_of: :parent
+        refs['ref1'] = {
+          '_type' => 'Child',
+          'name' => 'newchildname',
+        }
+      end
+
+      assert_equal(3, model.children.size)
+      assert_equal('newchildname', model.children.last.name)
+    end
+
+    it 'updates with removing a child' do
+      model = create_model!
+      old_child = model.children.last
+
+      alter_by_view!(ModelView, model) do |view, refs|
+        removed = view['children'].pop['_ref']
+        refs.delete(removed)
+      end
+
+      assert_equal(1, model.children.size)
+      assert_equal('c1', model.children.first.name)
+      assert_empty(child_model_class.where(id: old_child.id))
+    end
+
+    it 'updates with removing a child functionally' do
+      model = create_model!
+      old_child = model.children.last
+
+      alter_by_view!(ModelView, model) do |view, refs|
+        removed_ref = view['children'].pop['_ref']
+        removed_id = refs[removed_ref]['id']
+        refs.clear
+
+        view['children'] = build_fupdate do
+          remove([{ '_type' => 'Child', 'id' => removed_id }])
+        end
+      end
+
+      assert_equal(1, model.children.size)
+      assert_equal('c1', model.children.first.name)
+      assert_empty(child_model_class.where(id: old_child.id))
+    end
+
+    it 'updates with replacing a child' do
+      model = create_model!
+      old_child = model.children.last
+
+      alter_by_view!(ModelView, model) do |view, refs|
+        exchange_ref = view['children'].last['_ref']
+        refs[exchange_ref] = {
+          '_type' => 'Child',
+          'name' => 'newchildname',
+        }
+      end
+
+      children = model.children.sort_by(&:position)
+      assert_equal(2, children.size)
+      refute_equal(old_child.id, children.last.id)
+      assert_equal('newchildname', children.last.name)
+      assert_empty(child_model_class.where(id: old_child.id))
+    end
+
+    it 'updates with replacing a child functionally' do
+      model = create_model!
+      old_child = model.children.first
+
+      alter_by_view!(ModelView, model) do |view, refs|
+        removed_ref = view['children'].shift['_ref']
+        removed_id = refs[removed_ref]['id']
+        refs.clear
+
+        view['children'] = build_fupdate do
+          append([{ '_ref' => 'repl_ref' }],
+                 after: { '_type' => 'Child', 'id' => removed_id })
+          remove([{ '_type' => 'Child', 'id' => removed_id }])
         end
 
-        define_viewmodel do
-          attributes :name
-          association :children, as: :something_else
+        refs['repl_ref'] = {
+          '_type' => 'Child',
+          'name' => 'newchildname',
+        }
+      end
+
+      children = model.children.sort_by(&:position)
+      assert_equal(2, children.size)
+      refute_equal(old_child.id, children.first.id)
+      assert_equal('newchildname', children.first.name)
+      assert_empty(child_model_class.where(id: old_child.id))
+    end
+
+    it 'updates with editing a child' do
+      model = create_model!
+
+      alter_by_view!(ModelView, model) do |view, refs|
+        c1ref = view['children'].first['_ref']
+        refs[c1ref]['name'] = 'renamed'
+      end
+
+      assert_equal(2, model.children.size)
+      assert_equal('renamed', model.children.first.name)
+    end
+
+    it 'updates with editing a child functionally' do
+      model = create_model!
+
+      alter_by_view!(ModelView, model) do |view, refs|
+        edit_ref = view['children'].shift['_ref']
+        refs.slice!(edit_ref)
+
+        view['children'] = build_fupdate do
+          update([{ '_ref' => edit_ref }])
         end
+
+        refs[edit_ref]['name'] = 'renamed'
+      end
+
+      assert_equal(2, model.children.size)
+      assert_equal('renamed', model.children.first.name)
+    end
+
+    describe 'with association manipulation' do
+      it 'appends a child' do
+        view = create_viewmodel!
+
+        view.append_associated(:children, { '_type' => 'Child', 'name' => 'newchildname' })
+
+        view.model.reload
+        assert_equal(3, view.children.size)
+        assert_equal('newchildname', view.children.last.name)
+      end
+
+      it 'inserts a child' do
+        view = create_viewmodel!
+        c1 = view.children.first
+
+        view.append_associated(:children,
+                               { '_type' => 'Child', 'name' => 'newchildname' },
+                               after: c1.to_reference)
+        view.model.reload
+
+        assert_equal(3, view.children.size)
+        assert_equal('newchildname', view.children[1].name)
+      end
+
+      it 'moves a child' do
+        view = create_viewmodel!
+        c1, c2 = view.children
+
+        view.append_associated(:children,
+                               { '_type' => 'Child', 'id' => c2.id },
+                               before: c1.to_reference)
+        view.model.reload
+
+        assert_equal(2, view.children.size)
+        assert_equal(['c2', 'c1'], view.children.map(&:name))
+      end
+
+      it 'replaces children' do
+        view = create_viewmodel!
+        view.replace_associated(:children,
+                                [{ '_type' => 'Child', 'name' => 'newchildname' }])
+
+        view.model.reload
+
+        assert_equal(1, view.children.size)
+        assert_equal('newchildname', view.children[0].name)
       end
 
-      ViewModel::ActiveRecord::HasManyTest.build_child(self)
+      it 'deletes a child' do
+        view = create_viewmodel!
+        view.delete_associated(:children, view.children.first.id)
+
+        view.model.reload
+
+        assert_equal(1, view.children.size)
+        assert_equal('c2', view.children[0].name)
+      end
+    end
+  end
+
+  describe 'renaming associations' do
+    def subject_association_features
+      { as: :something_else }
     end
 
     def setup
       super
 
-      @parent = Parent.create(name: 'p1', children: [Child.new(name: 'c1')])
+      @model = model_class.create(name: 'p1', children: [child_model_class.new(name: 'c1', position: 0)])
 
       enable_logging!
     end
 
     def test_dependencies
-      root_updates, _ref_updates = ViewModel::ActiveRecord::UpdateData.parse_hashes([{ '_type' => 'Parent', 'something_else' => [] }])
+      root_updates, _ref_updates = ViewModel::ActiveRecord::UpdateData.parse_hashes([{ '_type' => 'Model', 'something_else' => [] }])
       assert_equal(DeepPreloader::Spec.new('children' => DeepPreloader::Spec.new), root_updates.first.preload_dependencies)
-      assert_equal({ 'something_else' => {} }, root_updates.first.updated_associations)
     end
 
     def test_renamed_roundtrip
-      alter_by_view!(ParentView, @parent) do |view, _refs|
-        assert_equal([{ 'id'       => @parent.children.first.id,
+      alter_by_view!(viewmodel_class, @model) do |view, _refs|
+        assert_equal([{ 'id'       => @model.children.first.id,
                         '_type'    => 'Child',
                         '_version' => 1,
                         'name'     => 'c1' }],
                      view['something_else'])
+
         view['something_else'][0]['name'] = 'new c1 name'
       end
 
-      assert_equal('new c1 name', @parent.children.first.name)
+      assert_equal('new c1 name', @model.children.first.name)
     end
   end
 end
diff --git a/test/unit/view_model/active_record/has_many_through_poly_test.rb b/test/unit/view_model/active_record/has_many_through_poly_test.rb
index 09cbec07..fb6023e5 100644
--- a/test/unit/view_model/active_record/has_many_through_poly_test.rb
+++ b/test/unit/view_model/active_record/has_many_through_poly_test.rb
@@ -20,6 +20,7 @@ def self.build_tag_a(arvm_test_case)
       end
 
       define_viewmodel do
+        root!
         attributes :name
       end
     end
@@ -37,6 +38,7 @@ def self.build_tag_b(arvm_test_case)
       end
 
       define_viewmodel do
+        root!
         attributes :name
       end
     end
@@ -53,8 +55,9 @@ def self.build_parent(arvm_test_case)
       end
 
       define_viewmodel do
+        root!
         attributes :name
-        association :tags, shared: true, through: :parents_tags, through_order_attr: :position, viewmodels: [TagAView, TagBView]
+        association :tags, through: :parents_tags, through_order_attr: :position, viewmodels: [TagAView, TagBView]
       end
     end
   end
@@ -86,10 +89,6 @@ def before_all
     self.class.build_parent_tag_join_model(self)
   end
 
-  private def context_with(*args)
-    ParentView.new_serialize_context(include: args)
-  end
-
   def setup
     super
 
@@ -108,14 +107,14 @@ def setup
   def test_roundtrip
     # Objects are serialized to a view and deserialized, and should not be different when complete.
 
-    alter_by_view!(ParentView, @parent1, serialize_context: context_with(:tags)) {}
+    alter_by_view!(ParentView, @parent1) {}
     assert_equal('p1', @parent1.name)
     assert_equal([@tag_a1, @tag_a2, @tag_b1, @tag_b2],
                  @parent1.parents_tags.order(:position).map(&:tag))
   end
 
   def test_loading_batching
-    context = context_with(:tags)
+    context = ParentView.new_serialize_context
     log_queries do
       parent_views = ParentView.load(serialize_context: context)
       serialize(parent_views, serialize_context: context)
@@ -126,7 +125,7 @@ def test_loading_batching
   end
 
   def test_eager_includes
-    includes = ParentView.eager_includes(serialize_context: context_with(:tags))
+    includes = ParentView.eager_includes
     assert_equal(DeepPreloader::Spec.new(
                   'parents_tags' => DeepPreloader::Spec.new(
                     'tag' => DeepPreloader::PolymorphicSpec.new(
@@ -157,8 +156,7 @@ def test_preload_dependencies
 
 
   def test_serialize
-    view, refs = serialize_with_references(ParentView.new(@parent1),
-                                           serialize_context: context_with(:tags))
+    view, refs = serialize_with_references(ParentView.new(@parent1))
 
     tag_data = view['tags'].map { |hash| refs[hash['_ref']] }
     assert_equal([{ 'id' => @tag_a1.id, '_type' => 'TagA', '_version' => 1, 'name' => 'tag A1' },
@@ -188,7 +186,7 @@ def test_create_has_many_through
   end
 
   def test_reordering_swap_type
-    alter_by_view!(ParentView, @parent1, serialize_context: context_with(:tags)) do |view, refs|
+    alter_by_view!(ParentView, @parent1) do |view, refs|
       t1, t2, t3, t4 = view['tags']
       view['tags'] = [t3, t2, t1, t4]
     end
@@ -223,8 +221,9 @@ def before_all
         end
 
         define_viewmodel do
+          root!
           attributes :name
-          association :tags, shared: true, through: :parents_tags, through_order_attr: :position, viewmodels: [TagAView, TagBView], as: :something_else
+          association :tags, through: :parents_tags, through_order_attr: :position, viewmodels: [TagAView, TagBView], as: :something_else
         end
       end
 
@@ -244,12 +243,10 @@ def test_dependencies
       # Compare to non-polymorphic, which will also load the tags
       deps = root_updates.first.preload_dependencies
       assert_equal(DeepPreloader::Spec.new('parents_tags' => DeepPreloader::Spec.new('tag' => DeepPreloader::PolymorphicSpec.new)), deps)
-      assert_equal({ 'something_else' => {} }, root_updates.first.updated_associations)
     end
 
-
     def test_renamed_roundtrip
-      context = ParentView.new_serialize_context(include: :something_else)
+      context = ParentView.new_serialize_context
       alter_by_view!(ParentView, @parent, serialize_context: context) do |view, refs|
         assert_equal({refs.keys.first => { 'id'       => @parent.parents_tags.first.tag.id,
                                            '_type'    => 'TagA',
diff --git a/test/unit/view_model/active_record/has_many_through_test.rb b/test/unit/view_model/active_record/has_many_through_test.rb
index 4e114636..47a80845 100644
--- a/test/unit/view_model/active_record/has_many_through_test.rb
+++ b/test/unit/view_model/active_record/has_many_through_test.rb
@@ -19,8 +19,9 @@ def self.build_parent(arvm_test_case)
       end
 
       define_viewmodel do
+        root!
         attributes :name
-        association :tags, shared: true, through: :parents_tags, through_order_attr: :position
+        association :tags, through: :parents_tags, through_order_attr: :position
       end
     end
   end
@@ -40,6 +41,7 @@ def self.build_tag(arvm_test_case, with: [])
       end
 
       define_viewmodel do
+        root!
         attributes :name
         if use_childtag
           associations :child_tags
@@ -91,10 +93,6 @@ def before_all
     self.class.build_join_table_model(self)
   end
 
-  private def context_with(*args)
-    ParentView.new_serialize_context(include: args)
-  end
-
   def setup
     super
 
@@ -108,7 +106,7 @@ def setup
   end
 
   def test_loading_batching
-    context = context_with(:tags)
+    context = ParentView.new_serialize_context
     log_queries do
       parent_views = ParentView.load(serialize_context: context)
       serialize(parent_views, serialize_context: context)
@@ -121,13 +119,13 @@ def test_loading_batching
   def test_roundtrip
     # Objects are serialized to a view and deserialized, and should not be different when complete.
 
-    alter_by_view!(ParentView, @parent1, serialize_context: context_with(:tags)) {}
+    alter_by_view!(ParentView, @parent1) {}
     assert_equal('p1', @parent1.name)
     assert_equal([@tag1, @tag2], @parent1.parents_tags.order(:position).map(&:tag))
   end
 
   def test_eager_includes
-    includes = ParentView.eager_includes(serialize_context: context_with(:tags))
+    includes = ParentView.eager_includes
     assert_equal(DeepPreloader::Spec.new('parents_tags' => DeepPreloader::Spec.new('tag' => DeepPreloader::Spec.new)), includes)
   end
 
@@ -150,21 +148,8 @@ def test_preload_dependencies
                  'mentioning tags and child_tags causes through association loading')
   end
 
-  def test_updated_associations
-    root_updates, _ref_updates = ViewModel::ActiveRecord::UpdateData.parse_hashes(
-      [{ '_type' => 'Parent',
-         'tags' => [{ '_ref' => 'r1' }] }],
-      { 'r1' => { '_type' => 'Tag', } })
-
-    assert_equal({ 'tags' => {} },
-                 root_updates.first.updated_associations,
-                 'mentioning tags causes through association loading')
-
-  end
-
   def test_serialize
-    view, refs = serialize_with_references(ParentView.new(@parent1),
-                                           serialize_context: context_with(:tags))
+    view, refs = serialize_with_references(ParentView.new(@parent1))
 
     tag_data = view['tags'].map { |hash| refs[hash['_ref']] }
     assert_equal([{ 'id' => @tag1.id, '_type' => 'Tag', '_version' => 1, 'name' => 'tag1' },
@@ -198,7 +183,7 @@ def test_delete
   end
 
   def test_reordering
-    pv, ctx = alter_by_view!(ParentView, @parent1, serialize_context: context_with(:tags)) do |view, _refs|
+    pv, ctx = alter_by_view!(ParentView, @parent1) do |view, _refs|
       view['tags'].reverse!
     end
 
@@ -211,7 +196,7 @@ def test_reordering
 
   def test_child_edit_doesnt_editcheck_parent
     # editing child doesn't edit check parent
-    pv, d_context = alter_by_view!(ParentView, @parent1, serialize_context: context_with(:tags)) do |view, refs|
+    pv, d_context = alter_by_view!(ParentView, @parent1) do |view, refs|
       refs[view['tags'][0]["_ref"]]["name"] = "changed"
     end
 
@@ -223,7 +208,7 @@ def test_child_edit_doesnt_editcheck_parent
   end
 
   def test_child_reordering_editchecks_parent
-    pv, d_context = alter_by_view!(ParentView, @parent1, serialize_context: context_with(:tags)) do |view, _refs|
+    pv, d_context = alter_by_view!(ParentView, @parent1) do |view, _refs|
       view['tags'].reverse!
     end
 
@@ -232,7 +217,7 @@ def test_child_reordering_editchecks_parent
   end
 
   def test_child_deletion_editchecks_parent
-    pv, d_context = alter_by_view!(ParentView, @parent1, serialize_context: context_with(:tags)) do |view, refs|
+    pv, d_context = alter_by_view!(ParentView, @parent1) do |view, refs|
       removed = view['tags'].pop['_ref']
       refs.delete(removed)
     end
@@ -242,7 +227,7 @@ def test_child_deletion_editchecks_parent
   end
 
   def test_child_addition_editchecks_parent
-    pv, d_context = alter_by_view!(ParentView, @parent1, serialize_context: context_with(:tags)) do |view, refs|
+    pv, d_context = alter_by_view!(ParentView, @parent1) do |view, refs|
       view['tags'] << { '_ref' => 't_new' }
       refs['t_new'] = { '_type' => 'Tag', 'name' => 'newest tag' }
     end
@@ -617,8 +602,9 @@ def before_all
         end
 
         define_viewmodel do
+          root!
           attributes :name
-          association :tags, shared: true, through: :parents_tags, through_order_attr: :position, as: :something_else
+          association :tags, through: :parents_tags, through_order_attr: :position, as: :something_else
         end
       end
 
@@ -638,11 +624,10 @@ def test_dependencies
       root_updates, _ref_updates = ViewModel::ActiveRecord::UpdateData.parse_hashes([{ '_type' => 'Parent', 'something_else' => [] }])
       assert_equal(DeepPreloader::Spec.new('parents_tags' => DeepPreloader::Spec.new('tag' => DeepPreloader::Spec.new)),
                    root_updates.first.preload_dependencies)
-      assert_equal({ 'something_else' => {} }, root_updates.first.updated_associations)
     end
 
     def test_renamed_roundtrip
-      context = ParentView.new_serialize_context(include: :something_else)
+      context = ParentView.new_serialize_context
       alter_by_view!(ParentView, @parent, serialize_context: context) do |view, refs|
         assert_equal({refs.keys.first => { 'id'       => @parent.parents_tags.first.tag.id,
                                            '_type'    => 'Tag',
@@ -703,34 +688,6 @@ def test_preload_dependencies_functional
                    root_updates.first.preload_dependencies,
                    'mentioning tags and child_tags in functional update value causes through association loading, ' \
                    'excluding shared')
-
-    end
-
-    def test_updated_associations
-      root_updates, _ref_updates = ViewModel::ActiveRecord::UpdateData.parse_hashes(
-        [{ '_type' => 'Parent',
-           'tags' => [{ '_ref' => 'r1' }] }],
-        { 'r1' => { '_type' => 'Tag', 'child_tags' => [] } })
-
-      assert_equal({ 'tags' => { } },
-                   root_updates.first.updated_associations,
-                   'mentioning tags and child_tags causes through association loading, excluding shared')
-    end
-
-    def test_updated_associations_functional
-      fupdate = build_fupdate do
-        append([{ '_ref' => 'r1' }])
-      end
-
-      root_updates, _ref_updates = ViewModel::ActiveRecord::UpdateData.parse_hashes(
-        [{ '_type' => 'Parent',
-           'tags'  => fupdate }],
-        { 'r1' => { '_type' => 'Tag', 'child_tags' => [] } })
-
-      assert_equal({ 'tags' => { } },
-                   root_updates.first.updated_associations,
-                   'mentioning tags and child_tags in functional_update causes through association loading, ' \
-                   'excluding shared')
     end
   end
 end
diff --git a/test/unit/view_model/active_record/has_one_test.rb b/test/unit/view_model/active_record/has_one_test.rb
index 81d83915..6bace6f0 100644
--- a/test/unit/view_model/active_record/has_one_test.rb
+++ b/test/unit/view_model/active_record/has_one_test.rb
@@ -1,5 +1,6 @@
 require_relative "../../../helpers/arvm_test_utilities.rb"
 require_relative "../../../helpers/arvm_test_models.rb"
+require_relative '../../../helpers/viewmodel_spec_helpers.rb'
 
 require "minitest/autorun"
 
@@ -8,80 +9,41 @@
 class ViewModel::ActiveRecord::HasOneTest < ActiveSupport::TestCase
   include ARVMTestUtilities
 
-  def self.build_target(arvm_test_case)
-    arvm_test_case.build_viewmodel(:Target) do
-      define_schema do |t|
-        t.string :text
-        t.references :parent, foreign_key: true
-      end
-
-      define_model do
-        belongs_to :parent, inverse_of: :target
-      end
-
-      define_viewmodel do
-        attributes :text
-      end
-    end
-  end
-
-
-  def self.build_parent(arvm_test_case)
-    arvm_test_case.build_viewmodel(:Parent) do
-      define_schema do |t|
-        t.string :name
-      end
-
-      define_model do
-        has_one    :target, dependent: :destroy, inverse_of: :parent
-      end
-
-      define_viewmodel do
-        attributes   :name
-        associations :target
-      end
-    end
-  end
-
-  def before_all
-    super
-
-    self.class.build_parent(self)
-    self.class.build_target(self)
-  end
+  extend Minitest::Spec::DSL
+  include ViewModelSpecHelpers::ParentAndHasOneChild
 
   def setup
     super
 
-    # TODO make a `has_list?` that allows a parent to set all children as an array
-    @parent1 = Parent.new(name: "p1",
-                          target: Target.new(text: "p1t"))
-    @parent1.save!
+    # TODO make a `has_list?` that allows a model to set all children as an array
+    @model1 = model_class.new(name: "p1",
+                          child: child_model_class.new(name: "p1t"))
+    @model1.save!
 
-    @parent2 = Parent.new(name: "p2",
-                          target: Target.new(text: "p2t"))
+    @model2 = model_class.new(name: "p2",
+                          child: child_model_class.new(name: "p2t"))
 
-    @parent2.save!
+    @model2.save!
 
     enable_logging!
   end
 
   def test_loading_batching
     log_queries do
-      serialize(ParentView.load)
+      serialize(ModelView.load)
     end
-    assert_equal(['Parent Load', 'Target Load'],
+    assert_equal(['Model Load', 'Child Load'],
                  logged_load_queries)
   end
 
   def test_create_from_view
     view = {
-      "_type"    => "Parent",
+      "_type"    => "Model",
       "name"     => "p",
-      "target"   => { "_type" => "Target", "text" => "t" },
+      "child"   => { "_type" => "Child", "name" => "t" },
     }
 
-    pv = ParentView.deserialize_from_view(view)
+    pv = ModelView.deserialize_from_view(view)
     p = pv.model
 
     assert(!p.changed?)
@@ -90,192 +52,383 @@ def test_create_from_view
     assert_equal("p", p.name)
 
 
-    assert(p.target.present?)
-    assert_equal("t", p.target.text)
+    assert(p.child.present?)
+    assert_equal("t", p.child.name)
   end
 
   def test_serialize_view
-    view, _refs = serialize_with_references(ParentView.new(@parent1))
-    assert_equal({ "_type"    => "Parent",
+    view, _refs = serialize_with_references(ModelView.new(@model1))
+    assert_equal({ "_type"    => "Model",
                    "_version" => 1,
-                   "id"       => @parent1.id,
-                   "name"     => @parent1.name,
-                   "target"   => { "_type"    => "Target",
+                   "id"       => @model1.id,
+                   "name"     => @model1.name,
+                   "child"   => { "_type"    => "Child",
                                    "_version" => 1,
-                                   "id"       => @parent1.target.id,
-                                   "text"     => @parent1.target.text } },
+                                   "id"       => @model1.child.id,
+                                   "name"     => @model1.child.name } },
                  view)
   end
 
   def test_swap_has_one
-    @parent1.update(target: t1 = Target.new)
-    @parent2.update(target: t2 = Target.new)
+    @model1.update(child: t1 = Child.new)
+    @model2.update(child: t2 = Child.new)
 
     deserialize_context = ViewModelBase.new_deserialize_context
 
-    ParentView.deserialize_from_view(
-      [update_hash_for(ParentView, @parent1) { |p| p['target'] = update_hash_for(TargetView, t2) },
-       update_hash_for(ParentView, @parent2) { |p| p['target'] = update_hash_for(TargetView, t1) }],
+    ModelView.deserialize_from_view(
+      [update_hash_for(ModelView, @model1) { |p| p['child'] = update_hash_for(ChildView, t2) },
+       update_hash_for(ModelView, @model2) { |p| p['child'] = update_hash_for(ChildView, t1) }],
       deserialize_context: deserialize_context)
 
-    assert_equal(Set.new([ViewModel::Reference.new(ParentView, @parent1.id),
-                          ViewModel::Reference.new(ParentView, @parent2.id)]),
+    assert_equal(Set.new([ViewModel::Reference.new(ModelView, @model1.id),
+                          ViewModel::Reference.new(ModelView, @model2.id)]),
                  deserialize_context.valid_edit_refs.to_set)
 
-    @parent1.reload
-    @parent2.reload
+    @model1.reload
+    @model2.reload
 
-    assert_equal(@parent1.target, t2)
-    assert_equal(@parent2.target, t1)
+    assert_equal(@model1.child, t2)
+    assert_equal(@model2.child, t1)
   end
 
   def test_has_one_create_nil
-    view = { '_type' => 'Parent', 'name' => 'p', 'target' => nil }
-    pv = ParentView.deserialize_from_view(view)
-    assert_nil(pv.model.target)
+    view = { '_type' => 'Model', 'name' => 'p', 'child' => nil }
+    pv = ModelView.deserialize_from_view(view)
+    assert_nil(pv.model.child)
   end
 
   def test_has_one_create
-    @parent1.update(target: nil)
+    @model1.update(child: nil)
 
-    alter_by_view!(ParentView, @parent1) do |view, refs|
-      view['target'] = { '_type' => 'Target', 'text' => 't' }
+    alter_by_view!(ModelView, @model1) do |view, refs|
+      view['child'] = { '_type' => 'Child', 'name' => 't' }
     end
 
-    assert_equal('t', @parent1.target.text)
+    assert_equal('t', @model1.child.name)
   end
 
   def test_has_one_update
-    alter_by_view!(ParentView, @parent1) do |view, refs|
-      view['target']['text'] = "hello"
+    alter_by_view!(ModelView, @model1) do |view, refs|
+      view['child']['name'] = "hello"
     end
 
-    assert_equal('hello', @parent1.target.text)
+    assert_equal('hello', @model1.child.name)
   end
 
   def test_has_one_destroy
-    old_target = @parent1.target
-    alter_by_view!(ParentView, @parent1) do |view, refs|
-      view['target'] = nil
+    old_child = @model1.child
+    alter_by_view!(ModelView, @model1) do |view, refs|
+      view['child'] = nil
     end
-    assert(Target.where(id: old_target.id).blank?)
+    assert(Child.where(id: old_child.id).blank?)
   end
 
   def test_has_one_move_and_replace
-    old_parent1_target = @parent1.target
-    old_parent2_target = @parent2.target
+    old_model1_child = @model1.child
+    old_model2_child = @model2.child
 
-    alter_by_view!(ParentView, [@parent1, @parent2]) do |(p1, p2), refs|
-      p2['target'] = p1['target']
-      p1['target'] = nil
+    alter_by_view!(ModelView, [@model1, @model2]) do |(p1, p2), refs|
+      p2['child'] = p1['child']
+      p1['child'] = nil
     end
 
-    assert(@parent1.target.blank?)
-    assert_equal(old_parent1_target, @parent2.target)
-    assert(Target.where(id: old_parent2_target).blank?)
+    assert(@model1.child.blank?)
+    assert_equal(old_model1_child, @model2.child)
+    assert(Child.where(id: old_model2_child).blank?)
   end
 
   def test_has_one_cannot_duplicate_unreleased_child
-    # p2 shouldn't be able to copy p1's target
+    # p2 shouldn't be able to copy p1's child
     assert_raises(ViewModel::DeserializationError::DuplicateNodes) do
-      alter_by_view!(ParentView, [@parent1, @parent2]) do |(p1, p2), _refs|
-        p2['target'] = p1['target'].dup
+      alter_by_view!(ModelView, [@model1, @model2]) do |(p1, p2), _refs|
+        p2['child'] = p1['child'].dup
       end
     end
   end
 
   def test_has_one_cannot_duplicate_implicitly_unreleased_child
-    # p2 shouldn't be able to copy p1's target, even when p1 doesn't explicitly
+    # p2 shouldn't be able to copy p1's child, even when p1 doesn't explicitly
     # specify the association
     assert_raises(ViewModel::DeserializationError::ParentNotFound) do
-      alter_by_view!(ParentView, [@parent1, @parent2]) do |(p1, p2), _refs|
-        p2['target'] = p1['target']
-        p1.delete('target')
+      alter_by_view!(ModelView, [@model1, @model2]) do |(p1, p2), _refs|
+        p2['child'] = p1['child']
+        p1.delete('child')
       end
     end
   end
 
   def test_has_one_cannot_take_from_outside_tree
-    t3 = Parent.create(target: Target.new(text: 'hi')).target
+    t3 = Model.create(child: Child.new(name: 'hi')).child
 
     assert_raises(ViewModel::DeserializationError::ParentNotFound) do
-      alter_by_view!(ParentView, [@parent1]) do |(p1), _refs|
-        p1['target'] = update_hash_for(TargetView, t3)
+      alter_by_view!(ModelView, [@model1]) do |(p1), _refs|
+        p1['child'] = update_hash_for(ChildView, t3)
       end
     end
   end
 
-  def test_has_one_cannot_take_unparented_from_outside_tree
-    t3 = Target.create(text: 'hi') # no parent
+  def test_has_one_cannot_take_unmodeled_from_outside_tree
+    t3 = Child.create(name: 'hi') # no model
 
     assert_raises(ViewModel::DeserializationError::ParentNotFound) do
-      alter_by_view!(ParentView, @parent1) do |p1, _refs|
-        p1['target'] = update_hash_for(TargetView, t3)
+      alter_by_view!(ModelView, @model1) do |p1, _refs|
+        p1['child'] = update_hash_for(ChildView, t3)
       end
     end
   end
 
   def test_bad_single_association
     view = {
-      "_type" => "Parent",
-      "target" => []
+      "_type" => "Model",
+      "child" => []
     }
     ex = assert_raises(ViewModel::DeserializationError::InvalidSyntax) do
-      ParentView.deserialize_from_view(view)
+      ModelView.deserialize_from_view(view)
     end
     assert_match(/not an object/, ex.message)
   end
 
+  describe 'owned reference child' do
+    def child_attributes
+      super.merge(viewmodel: ->(v) { root! })
+    end
 
-  class RenameTest < ActiveSupport::TestCase
-    include ARVMTestUtilities
+    def new_model
+      model_class.new(name: 'm1', child: child_model_class.new(name: 'c1'))
+    end
 
-    def before_all
-      super
+    it 'makes a reference association' do
+      assert(subject_association.referenced?)
+    end
 
-      build_viewmodel(:Parent) do
-        define_schema do |t|
-          t.string :name
+    it 'makes an owned association' do
+      assert(subject_association.owned?)
+    end
+
+    it 'loads and batches' do
+      create_model!
+
+      log_queries do
+        serialize(ModelView.load)
+      end
+
+      assert_equal(['Model Load', 'Child Load'], logged_load_queries)
+    end
+
+    it 'serializes' do
+      model = create_model!
+      view, refs = serialize_with_references(ModelView.new(model))
+      child1_ref = refs.detect { |_, v| v['_type'] == 'Child' }.first
+
+      assert_equal({ child1_ref => { '_type'    => 'Child',
+                                     '_version' => 1,
+                                     'id'       => model.child.id,
+                                     'name'     => model.child.name } },
+                   refs)
+
+      assert_equal({ '_type'    => 'Model',
+                     '_version' => 1,
+                     'id'       => model.id,
+                     'name'     => model.name,
+                     'child' => { '_ref' => child1_ref } },
+                   view)
+    end
+
+    it 'creates from view' do
+      view = {
+        '_type' => 'Model',
+        'name'  => 'p',
+        'child' => { '_ref' => 'r1' },
+      }
+
+      refs = {
+        'r1' => { '_type' => 'Child', 'name' => 'newkid' },
+      }
+
+      pv = ModelView.deserialize_from_view(view, references: refs)
+      p = pv.model
+
+      assert(!p.changed?)
+      assert(!p.new_record?)
+
+      assert_equal('p', p.name)
+
+      assert(p.child.present?)
+      assert_equal('newkid', p.child.name)
+    end
+
+    it 'updates' do
+      model = create_model!
+
+      alter_by_view!(ModelView, model) do |view, refs|
+        ref = view['child']['_ref']
+        refs[ref]['name'] = 'newchildname'
+      end
+
+      assert_equal('newchildname', model.child.name)
+    end
+
+    describe 'without a child' do
+      let(:new_model) {
+        model_class.new(name: 'm1', child: nil)
+      }
+
+      it 'can add a child' do
+        model = create_model!
+
+        alter_by_view!(ModelView, model) do |view, refs|
+          view['child'] = { '_ref' => 'ref1' }
+          refs['ref1'] = {
+            '_type' => 'Child',
+            'name' => 'newchildname',
+          }
         end
 
-        define_model do
-          has_one    :target, dependent: :destroy, inverse_of: :parent
+        assert(model.child.present?)
+        assert_equal('newchildname', model.child.name)
+      end
+    end
+
+    it 'replaces a child with a new child' do
+      model = create_model!
+      old_child = model.child
+
+      alter_by_view!(ModelView, model) do |view, refs|
+        ref = view['child']['_ref']
+        refs[ref] = { '_type' => 'Child', 'name' => 'newchildname' }
+      end
+      model.reload
+
+      assert_equal('newchildname', model.child.name)
+      refute_equal(old_child, model.child)
+      assert(Child.where(id: old_child.id).blank?)
+    end
+
+    it 'takes a released child from another parent' do
+      model1 = create_model!
+      model2 = create_model!
+
+      old_child1 = model1.child
+      old_child2 = model2.child
+
+      alter_by_view!(ModelView, [model1, model2]) do |(view1, view2), refs|
+        ref1 = view1['child']['_ref']
+        ref2 = view2['child']['_ref']
+        refs.delete(ref1)
+        view1['child'] = { '_ref' => ref2 }
+        view2['child'] = nil
+      end
+
+      assert_equal(model1.child, old_child2)
+      assert_nil(model2.child)
+      assert(Child.where(id: old_child1.id).blank?)
+    end
+
+    it 'prevents taking an unreleased reference out-of-tree' do
+      model1 = create_model!
+      child2 = Child.create!(name: 'dummy')
+
+      assert_raises(ViewModel::DeserializationError::ParentNotFound) do
+        alter_by_view!(ModelView, model1) do |view, refs|
+          refs.clear
+          view['child']['_ref'] = 'r1'
+          refs['r1'] = { '_type' => 'Child', 'id' => child2.id }
         end
+      end
+    end
 
-        define_viewmodel do
-          attributes   :name
-          association :target, as: :something_else
+    it 'prevents taking an unreleased reference in-tree' do
+      model1 = create_model!
+      model2 = create_model!
+
+      assert_raises(ViewModel::DeserializationError::DuplicateOwner) do
+        alter_by_view!(ModelView, [model1, model2]) do |(view1, view2), refs|
+          refs.delete(view1['child']['_ref'])
+          view1['child']['_ref'] = view2['child']['_ref']
         end
       end
+    end
+
+    it 'prevents two parents taking the same new reference' do
+      model1 = create_model!
+      model2 = create_model!
+
+      assert_raises(ViewModel::DeserializationError::DuplicateOwner) do
+        alter_by_view!(ModelView, [model1, model2]) do |(view1, view2), refs|
+          refs.clear
+          refs['ref1'] = { '_type' => 'Child', 'name' => 'new' }
+          view1['child']['_ref'] = 'ref1'
+          view2['child']['_ref'] = 'ref1'
+        end
+      end
+    end
+
+    it 'swaps children' do
+      model1 = create_model!
+      model2 = create_model!
+
+      old_child1 = model1.child
+      old_child2 = model2.child
+
+      alter_by_view!(ModelView, [model1, model2]) do |(view1, view2), _refs|
+        ref1 = view1['child']
+        ref2 = view2['child']
+        view1['child'] = ref2
+        view2['child'] = ref1
+      end
+
+      assert_equal(model1.child, old_child2)
+      assert_equal(model2.child, old_child1)
+    end
+
+    it 'deletes a child' do
+      model = create_model!
+      old_child = model.child
+
+      alter_by_view!(ModelView, model) do |view, refs|
+        refs.clear
+        view['child'] = nil
+      end
+
+      assert_nil(model.child)
+      assert(Child.where(id: old_child.id).blank?)
+    end
+
+    it 'eager includes' do
+      includes = viewmodel_class.eager_includes
+      assert_equal(DeepPreloader::Spec.new('child' => DeepPreloader::Spec.new), includes)
+    end
+  end
 
-      ViewModel::ActiveRecord::HasOneTest.build_target(self)
+  describe 'renaming associations' do
+    def subject_association_features
+      { as: :something_else }
     end
 
     def setup
       super
 
-      @parent = Parent.create(target: Target.new(text: 'target text'))
+      @model = model_class.create(child: child_model_class.new(name: 'child name'))
 
       enable_logging!
     end
 
     def test_dependencies
-      root_updates, _ref_updates = ViewModel::ActiveRecord::UpdateData.parse_hashes([{ '_type' => 'Parent', 'something_else' => nil }])
-      assert_equal(DeepPreloader::Spec.new('target' => DeepPreloader::Spec.new), root_updates.first.preload_dependencies)
-      assert_equal({ 'something_else' => {} }, root_updates.first.updated_associations)
+      root_updates, _ref_updates = ViewModel::ActiveRecord::UpdateData.parse_hashes([{ '_type' => 'Model', 'something_else' => nil }])
+      assert_equal(DeepPreloader::Spec.new('child' => DeepPreloader::Spec.new), root_updates.first.preload_dependencies)
     end
 
     def test_renamed_roundtrip
-      alter_by_view!(ParentView, @parent) do |view, refs|
-        assert_equal({ 'id'       => @parent.target.id,
-                       '_type'    => 'Target',
+      alter_by_view!(ModelView, @model) do |view, refs|
+        assert_equal({ 'id'       => @model.child.id,
+                       '_type'    => 'Child',
                        '_version' => 1,
-                       'text'     => 'target text' },
+                       'name'     => 'child name' },
                      view['something_else'])
-        view['something_else']['text'] = 'target new text'
+        view['something_else']['name'] = 'child new name'
       end
 
-      assert_equal('target new text',  @parent.target.text)
+      assert_equal('child new name',  @model.child.name)
     end
   end
 
diff --git a/test/unit/view_model/active_record/optional_attribute_view_test.rb b/test/unit/view_model/active_record/optional_attribute_view_test.rb
deleted file mode 100644
index fd4e3bd3..00000000
--- a/test/unit/view_model/active_record/optional_attribute_view_test.rb
+++ /dev/null
@@ -1,58 +0,0 @@
-require_relative "../../../helpers/arvm_test_utilities.rb"
-require_relative "../../../helpers/arvm_test_models.rb"
-
-require "minitest/autorun"
-
-require "view_model/active_record"
-
-class ViewModel::ActiveRecord::AttributeViewTest < ActiveSupport::TestCase
-  include ARVMTestUtilities
-
-  def before_all
-    super
-
-    build_viewmodel(:Thing) do
-      define_schema do |t|
-        t.integer :a
-        t.integer :b
-      end
-
-      define_model do
-      end
-
-      define_viewmodel do
-        attribute :a
-        attribute :b, optional: true
-      end
-    end
-  end
-
-  def setup
-    super
-    @thing = Thing.create!(a: 1, b: 2)
-
-    @skel = { "_type"    => "Thing",
-              "_version" => 1,
-              "id"       => @thing.id }
-  end
-
-  def test_optional_not_serialized
-    view, _refs = serialize_with_references(ThingView.new(@thing))
-
-    assert_equal(@skel.merge("a" => 1), view)
-  end
-
-  def test_optional_included
-    view, _refs = serialize_with_references(ThingView.new(@thing),
-                                            serialize_context: ThingView.new_serialize_context(include: :b))
-
-    assert_equal(@skel.merge("a" => 1, "b" => 2), view)
-  end
-
-  def test_pruned_not_included
-    view, _refs = serialize_with_references(ThingView.new(@thing),
-                                            serialize_context: ThingView.new_serialize_context(include: :b, prune: :a))
-
-    assert_equal(@skel.merge("b" => 2), view)
-  end
-end
diff --git a/test/unit/view_model/active_record/poly_test.rb b/test/unit/view_model/active_record/poly_test.rb
index 83bdea2f..9cb6352a 100644
--- a/test/unit/view_model/active_record/poly_test.rb
+++ b/test/unit/view_model/active_record/poly_test.rb
@@ -299,7 +299,6 @@ def setup
       def test_dependencies
         root_updates, _ref_updates = ViewModel::ActiveRecord::UpdateData.parse_hashes([{ '_type' => 'Parent', 'something_else' => nil }])
         assert_equal(DeepPreloader::Spec.new('poly' => DeepPreloader::PolymorphicSpec.new), root_updates.first.preload_dependencies)
-        assert_equal({ 'something_else' => {} }, root_updates.first.updated_associations)
       end
 
       def test_renamed_roundtrip
diff --git a/test/unit/view_model/active_record/shared_test.rb b/test/unit/view_model/active_record/shared_test.rb
index 324ac0c1..4a5f134d 100644
--- a/test/unit/view_model/active_record/shared_test.rb
+++ b/test/unit/view_model/active_record/shared_test.rb
@@ -22,6 +22,7 @@ def before_all
         end
 
         define_viewmodel do
+          root!
           attributes :name
         end
       end
@@ -43,8 +44,9 @@ def before_all
         end
 
         define_viewmodel do
+          root!
           attributes  :name
-          association :category, shared: true, optional: true
+          association :category
         end
       end
     end
@@ -66,16 +68,11 @@ def setup
     enable_logging!
   end
 
-  def serialize_context
-    ParentView.new_serialize_context(include: :category)
-  end
-
   def test_loading_batching
     Parent.create(category: Category.new)
 
     log_queries do
-      serialize(ParentView.load(serialize_context: serialize_context),
-                serialize_context: serialize_context)
+      serialize(ParentView.load())
     end
     assert_equal(['Parent Load', 'Category Load'],
                  logged_load_queries)
@@ -104,7 +101,7 @@ def test_create_from_view
   end
 
   def test_serialize_view
-    view, refs = serialize_with_references(ParentView.new(@parent1), serialize_context: serialize_context)
+    view, refs = serialize_with_references(ParentView.new(@parent1))
     cat1_ref = refs.detect { |_, v| v['_type'] == 'Category' }.first
 
     assert_equal({cat1_ref => { '_type'    => "Category",
@@ -122,20 +119,14 @@ def test_serialize_view
   end
 
   def test_shared_eager_include
-    parent_includes = ParentView.eager_includes
-
-    assert_equal(DeepPreloader::Spec.new, parent_includes)
-
-    extra_includes = ParentView.eager_includes(serialize_context: ParentView.new_serialize_context(include: :category))
-
-    assert_equal(DeepPreloader::Spec.new('category' => DeepPreloader::Spec.new), extra_includes)
+    includes = ParentView.eager_includes
+    assert_equal(DeepPreloader::Spec.new('category' => DeepPreloader::Spec.new), includes)
   end
 
   def test_shared_serialize_interning
     @parent2.update(category: @parent1.category)
     view, refs = serialize_with_references([ParentView.new(@parent1),
-                                            ParentView.new(@parent2)],
-                                           serialize_context: ParentView.new_serialize_context(include: :category))
+                                            ParentView.new(@parent2)])
 
     category_ref = view.first['category']['_ref']
 
@@ -144,7 +135,7 @@ def test_shared_serialize_interning
   end
 
   def test_shared_add_reference
-    alter_by_view!(ParentView, @parent2, serialize_context: serialize_context) do |p2view, refs|
+    alter_by_view!(ParentView, @parent2) do |p2view, refs|
       p2view['category'] = { '_ref' => 'myref' }
       refs['myref'] = update_hash_for(CategoryView, @category1)
     end
@@ -153,7 +144,7 @@ def test_shared_add_reference
   end
 
   def test_shared_add_multiple_references
-    alter_by_view!(ParentView, [@parent1, @parent2], serialize_context: serialize_context) do |(p1view, p2view), refs|
+    alter_by_view!(ParentView, [@parent1, @parent2]) do |(p1view, p2view), refs|
       refs.delete(p1view['category']['_ref'])
       refs['myref'] = update_hash_for(CategoryView, @category1)
 
@@ -167,7 +158,7 @@ def test_shared_add_multiple_references
 
   def test_shared_requires_all_references
     ex = assert_raises(ViewModel::DeserializationError::InvalidStructure) do
-      alter_by_view!(ParentView, @parent2, serialize_context: serialize_context) do |p2view, refs|
+      alter_by_view!(ParentView, @parent2) do |p2view, refs|
         refs['spurious_ref'] = { '_type' => 'Parent', 'id' => @parent1.id }
       end
     end
@@ -176,8 +167,7 @@ def test_shared_requires_all_references
 
   def test_shared_requires_valid_references
     assert_raises(ViewModel::DeserializationError::InvalidSharedReference) do
-      serialize_context = ParentView.new_serialize_context(include: :category)
-      alter_by_view!(ParentView, @parent1, serialize_context: serialize_context) do |p1view, refs|
+      alter_by_view!(ParentView, @parent1) do |p1view, refs|
         refs.clear # remove the expected serialized refs
       end
     end
@@ -185,8 +175,7 @@ def test_shared_requires_valid_references
 
   def test_shared_requires_assignable_type
     ex = assert_raises(ViewModel::DeserializationError::InvalidAssociationType) do
-      serialize_context = ParentView.new_serialize_context(include: :category)
-      alter_by_view!(ParentView, @parent1, serialize_context: serialize_context) do |p1view, refs|
+      alter_by_view!(ParentView, @parent1) do |p1view, refs|
         p1view['category'] = { '_ref' => 'p2' }
         refs['p2'] = update_hash_for(ParentView, @parent2)
       end
@@ -195,10 +184,9 @@ def test_shared_requires_assignable_type
   end
 
   def test_shared_requires_unique_references
-    serialize_context = ParentView.new_serialize_context(include: :category)
     c1_ref = update_hash_for(CategoryView, @category1)
     assert_raises(ViewModel::DeserializationError::DuplicateNodes) do
-      alter_by_view!(ParentView, [@parent1, @parent2], serialize_context: serialize_context) do |(p1view, p2view), refs|
+      alter_by_view!(ParentView, [@parent1, @parent2]) do |(p1view, p2view), refs|
         refs['c_a'] = c1_ref.dup
         refs['c_b'] = c1_ref.dup
         p1view['category'] = { '_ref' => 'c_a' }
@@ -208,8 +196,7 @@ def test_shared_requires_unique_references
   end
 
   def test_shared_updates_shared_data
-    serialize_context = ParentView.new_serialize_context(include: :category)
-    alter_by_view!(ParentView, @parent1, serialize_context: serialize_context) do |p1view, refs|
+    alter_by_view!(ParentView, @parent1) do |p1view, refs|
       category_ref = p1view['category']['_ref']
       refs[category_ref]['name'] = 'newcatname'
     end
@@ -217,8 +204,7 @@ def test_shared_updates_shared_data
   end
 
   def test_shared_delete_reference
-    serialize_context = ParentView.new_serialize_context(include: :category)
-    alter_by_view!(ParentView, @parent1, serialize_context: serialize_context) do |p1view, refs|
+    alter_by_view!(ParentView, @parent1) do |p1view, refs|
       category_ref = p1view['category']['_ref']
       refs.delete(category_ref)
       p1view['category'] = nil
@@ -228,10 +214,9 @@ def test_shared_delete_reference
   end
 
   def test_child_edit_doesnt_editcheck_parent
-    serialize_context = ParentView.new_serialize_context(include: :category)
     d_context = ParentView.new_deserialize_context
 
-    alter_by_view!(ParentView, @parent1, serialize_context: serialize_context, deserialize_context: d_context) do |view, refs|
+    alter_by_view!(ParentView, @parent1, deserialize_context: d_context) do |view, refs|
       refs[view['category']["_ref"]]["name"] = "changed"
     end
 
@@ -240,9 +225,7 @@ def test_child_edit_doesnt_editcheck_parent
   end
 
   def test_child_change_editchecks_parent
-    s_context = ParentView.new_serialize_context(include: :category)
-
-    nv, d_context = alter_by_view!(ParentView, @parent1, serialize_context: s_context) do |view, refs|
+    nv, d_context = alter_by_view!(ParentView, @parent1) do |view, refs|
       refs.delete(view['category']['_ref'])
       view['category']['_ref'] = 'new_cat'
       refs['new_cat'] = { '_type' => 'Category', 'name' => 'new category' }
@@ -253,10 +236,9 @@ def test_child_change_editchecks_parent
   end
 
   def test_child_delete_editchecks_parent
-    serialize_context = ParentView.new_serialize_context(include: :category)
     d_context = ParentView.new_deserialize_context
 
-    alter_by_view!(ParentView, @parent1, serialize_context: serialize_context, deserialize_context: d_context) do |view, refs|
+    alter_by_view!(ParentView, @parent1, deserialize_context: d_context) do |view, refs|
       refs.delete(view['category']['_ref'])
       view['category'] = nil
     end
@@ -268,7 +250,7 @@ def test_dependent_viewmodels
     deps = ParentView.dependent_viewmodels
     assert_equal([ParentView, CategoryView].to_set, deps)
 
-    deps = ParentView.dependent_viewmodels(include_shared: false)
+    deps = ParentView.dependent_viewmodels(include_referenced: false)
     assert_equal([ParentView].to_set, deps)
   end
 
@@ -278,7 +260,7 @@ def test_deep_schema_version
                    CategoryView.view_name => CategoryView.schema_version },
                  vers)
 
-    vers = ParentView.deep_schema_version(include_shared: false)
+    vers = ParentView.deep_schema_version(include_referenced: false)
     assert_equal({ ParentView.view_name => ParentView.schema_version },
                  vers)
   end
diff --git a/test/unit/view_model/active_record/version_test.rb b/test/unit/view_model/active_record/version_test.rb
index 588df0ab..3b04176e 100644
--- a/test/unit/view_model/active_record/version_test.rb
+++ b/test/unit/view_model/active_record/version_test.rb
@@ -21,13 +21,13 @@ def before_all
       end
     end
 
-
     build_viewmodel(:Target) do
       define_schema {}
       define_model do
         has_one :parent, inverse_of: :target
       end
       define_viewmodel do
+        root!
         self.schema_version = 20
       end
     end
@@ -44,8 +44,9 @@ def before_all
       end
       define_viewmodel do
         self.schema_version = 5
+        root!
         association :child, viewmodels: [:ChildA]
-        association :target, shared: true, optional: false
+        association :target
       end
     end
   end
diff --git a/test/unit/view_model/active_record_test.rb b/test/unit/view_model/active_record_test.rb
index b10a4846..099cc8c5 100644
--- a/test/unit/view_model/active_record_test.rb
+++ b/test/unit/view_model/active_record_test.rb
@@ -17,7 +17,7 @@ def before_all
     build_viewmodel(:Trivial) do
       define_schema
       define_model {}
-      define_viewmodel {}
+      define_viewmodel { root! }
     end
 
     build_viewmodel(:Parent) do
@@ -35,6 +35,7 @@ def before_all
       end
 
       define_viewmodel do
+        root!
         attributes :name, :lock_version
         attribute :one, read_only: true
       end
@@ -376,66 +377,6 @@ def test_create
     end
   end
 
-  # Tests for functionality common to all ARVM instances, but require some kind
-  # of relationship.
-  class RelationshipTests < ActiveSupport::TestCase
-    include ARVMTestUtilities
-
-    def before_all
-      super
-
-      build_viewmodel(:Parent) do
-        define_schema do |t|
-          t.string :name
-        end
-
-        define_model do
-          has_many :children, dependent: :destroy, inverse_of: :parent
-        end
-
-        define_viewmodel do
-          attributes :name
-          associations :children
-        end
-      end
-
-      build_viewmodel(:Child) do
-        define_schema do |t|
-          t.references :parent, null: false, foreign_key: true
-          t.string :name
-        end
-
-        define_model do
-          belongs_to :parent, inverse_of: :children
-        end
-
-        define_viewmodel do
-          attributes :name
-        end
-      end
-    end
-
-    def test_updated_associations_returned
-      # This test ensures the data is passed back through the context. The tests
-      # for the values are in the relationship-specific tests.
-
-      updated_by_view = ->(view) do
-        context = ViewModelBase.new_deserialize_context
-        ParentView.deserialize_from_view(view, deserialize_context: context)
-        context.updated_associations
-      end
-
-      assert_equal({},
-                   updated_by_view.({ '_type' => 'Parent',
-                                      'name' => 'p' }))
-
-      assert_equal({ 'children' => {} },
-                   updated_by_view.({ '_type' => 'Parent',
-                                      'name' => 'p',
-                                      'children' => [] }))
-    end
-  end
-
   # Parent view should be correctly passed down the tree when deserializing
   class DeserializationParentContextTest < ActiveSupport::TestCase
     include ARVMTestUtilities
@@ -499,7 +440,7 @@ def test_deserialize_context
     end
   end
 
-    # Parent view should be correctly passed down the tree when deserializing
+  # Parent view should be correctly passed down the tree when deserializing
   class DeferredConstraintTest < ActiveSupport::TestCase
     include ARVMTestUtilities
 
@@ -516,7 +457,8 @@ def before_all
         end
 
         define_viewmodel do
-          association :child, shared: true
+          root!
+          association :child
         end
       end
       List.connection.execute("ALTER TABLE lists ADD CONSTRAINT unique_child UNIQUE (child_id) DEFERRABLE INITIALLY DEFERRED")
diff --git a/test/unit/view_model/callbacks_test.rb b/test/unit/view_model/callbacks_test.rb
index 18e9d001..aae3a68b 100644
--- a/test/unit/view_model/callbacks_test.rb
+++ b/test/unit/view_model/callbacks_test.rb
@@ -348,6 +348,7 @@ def new_model
         alter_by_view!(viewmodel_class, vm.model) do |view, _refs|
           view['next'] = nil
         end
+
         value(callback.hook_trace).must_equal(
           [
             visit(ViewModel::Callbacks::Hook::BeforeVisit,       vm),
diff --git a/test/unit/view_model/record_test.rb b/test/unit/view_model/record_test.rb
index 967406fe..cdec9c32 100644
--- a/test/unit/view_model/record_test.rb
+++ b/test/unit/view_model/record_test.rb
@@ -204,12 +204,6 @@ def self.included(base)
         assert_equal("unknown", ex.attribute)
       end
 
-      it "can prune an attribute" do
-        h = viewmodel_class.new(default_model).to_hash(serialize_context: TestSerializeContext.new(prune: [:simple]))
-        pruned_view = default_view.tap { |v| v.delete("simple") }
-        assert_equal(pruned_view, h)
-      end
-
       it "edit checks when creating empty" do
         vm = viewmodel_class.deserialize_from_view(view_base, deserialize_context: create_context)
         refute(default_model.equal?(vm.model), "returned model was the same")
@@ -377,24 +371,6 @@ def deserialize_overridden(value, references:, deserialize_context:)
       end
     end
 
-    describe "with optional attributes" do
-      let(:attributes) { { optional: { optional: true } } }
-
-      include CanDeserializeToNew
-      include CanDeserializeToExisting
-
-      it "can serialize with the optional attribute" do
-        h = viewmodel_class.new(default_model).to_hash(serialize_context: TestSerializeContext.new(include: [:optional]))
-        assert_equal(default_view, h)
-      end
-
-      it "can serialize without the optional attribute" do
-        h = viewmodel_class.new(default_model).to_hash
-        pruned_view = default_view.tap { |v| v.delete("optional") }
-        assert_equal(pruned_view, h)
-      end
-    end
-
     Nested = Struct.new(:member)
 
     class NestedView < TestViewModel
@@ -448,14 +424,6 @@ class NestedView < TestViewModel
         assert_edited(vm, new: false, changed_attributes: [:nested])
         assert_edited(vm.nested, new: true, changed_attributes: [:member])
       end
-
-      it "can prune attributes in the nested value" do
-        h = viewmodel_class.new(default_model).to_hash(
-          serialize_context: TestSerializeContext.new(prune: { nested: [:member] }))
-
-        pruned_view = default_view.tap { |v| v["nested"].delete("member") }
-        assert_equal(pruned_view, h)
-      end
     end
 
     describe "with array of nested viewmodel" do
diff --git a/test/unit/view_model/traversal_context_test.rb b/test/unit/view_model/traversal_context_test.rb
index a4dc926c..4997bbc6 100644
--- a/test/unit/view_model/traversal_context_test.rb
+++ b/test/unit/view_model/traversal_context_test.rb
@@ -35,6 +35,7 @@ def initialize
     after_visit do
       ref = view.to_reference
       raise RuntimeError.new('Visited twice') if details.has_key?(ref)
+
       details[ref] = ContextDetail.new(
         context.parent_viewmodel&.to_reference,
         context.parent_association,
@@ -87,12 +88,12 @@ def assert_traversal_matches(expected_details, recorded_details)
     # models have no more than one shared association, and if present it is the
     # one under test.
     def clear_subject_association(view, refs)
-      refs.clear if subject_association.shared?
+      refs.clear if subject_association.referenced?
       view[subject_association_name] = subject_association.collection? ? [] : nil
     end
 
     def set_subject_association(view, refs, value)
-      if subject_association.shared?
+      if subject_association.referenced?
         refs.clear
         value = convert_to_refs(refs, value)
       end
@@ -100,7 +101,7 @@ def set_subject_association(view, refs, value)
     end
 
     def add_to_subject_association(view, refs, value)
-      if subject_association.shared?
+      if subject_association.referenced?
         value = convert_to_refs(refs, value)
       end
       view[subject_association_name] << value
@@ -108,12 +109,12 @@ def add_to_subject_association(view, refs, value)
 
     def remove_from_subject_association(view, refs)
       view[subject_association_name].reject! do |child|
-        if subject_association.shared?
+        if subject_association.referenced?
           ref = child[ViewModel::REFERENCE_ATTRIBUTE]
           child = refs[ref]
         end
         match = yield(child)
-        if match && subject_association.shared?
+        if match && subject_association.referenced?
           refs.delete(ref)
         end
         match
@@ -167,7 +168,7 @@ def self.included(base)
           end
 
           expected = expected_parent_details
-          expected = expected.merge(expected_children_details) unless subject_association.shared?
+          expected = expected.merge(expected_children_details) unless subject_association.referenced?
           assert_traversal_matches(expected, context_recorder.details)
         end
 
@@ -179,7 +180,7 @@ def self.included(base)
           end
 
           expected = expected_parent_details
-          expected = expected.merge(expected_children_details) unless subject_association.shared?
+          expected = expected.merge(expected_children_details) unless subject_association.referenced?
           expected = expected.merge(new_child_expected_details)
           assert_traversal_matches(expected, context_recorder.details)
         end
@@ -190,7 +191,7 @@ def self.included(base)
           vm.replace_associated(subject_association_name, replacement, deserialize_context: ctx)
 
           expected = expected_parent_details
-          expected = expected.merge(expected_children_details) unless subject_association.shared?
+          expected = expected.merge(expected_children_details) unless subject_association.referenced?
           expected = expected.merge(new_child_expected_details)
           assert_traversal_matches(expected, context_recorder.details)
         end
@@ -224,7 +225,7 @@ def self.included(base)
           end
 
           expected = expected_parent_details.merge(expected_children_details)
-          expected = expected.except(removed_child.to_reference) if subject_association.shared?
+          expected = expected.except(removed_child.to_reference) if subject_association.referenced?
           assert_traversal_matches(expected, context_recorder.details)
         end
 
@@ -241,7 +242,7 @@ def self.included(base)
           vm.delete_associated(subject_association_name, removed_child.id, deserialize_context: ctx)
 
           expected = expected_parent_details
-          expected = expected.merge(removed_child_expected_details) unless subject_association.shared?
+          expected = expected.merge(removed_child_expected_details) unless subject_association.referenced?
           assert_traversal_matches(expected, context_recorder.details)
         end
       end
@@ -265,7 +266,7 @@ def self.included(base)
 
   let(:root_detail) { ContextDetail.new(nil, nil, true) }
   let(:child_detail) do
-    if subject_association.shared?
+    if subject_association.referenced?
       root_detail
     else
       ContextDetail.new(vm.to_reference, subject_association_name, false)
@@ -346,7 +347,7 @@ def self.included(base)
   end
 
   describe 'with parent and shared child' do
-    include ViewModelSpecHelpers::ParentAndSharedChild
+    include ViewModelSpecHelpers::ParentAndSharedBelongsToChild
 
     include BehavesLikeSerialization
     include BehavesLikeDeserialization