diff --git a/scopegraphs/src/containers/env.rs b/scopegraphs/src/containers/env.rs
index 990c68d..60e8e7a 100644
--- a/scopegraphs/src/containers/env.rs
+++ b/scopegraphs/src/containers/env.rs
@@ -1,7 +1,6 @@
 use crate::future_wrapper::FutureWrapper;
 use crate::resolve::{Env, ResolvedPath};
 use futures::future::Shared;
-use futures::io::empty;
 use std::hash::Hash;
 use std::rc::Rc;
 
@@ -12,7 +11,7 @@ pub trait EnvContainer<'sg, 'rslv, LABEL: 'sg, DATA: 'sg, DWFO>:
     /// Creates a new, container with an empty environment.
     fn empty() -> Self;
 
-    fn inject_if(data_ok: DWFO, path: ResolvedPath<LABEL, DATA>) -> Self;
+    fn inject_if(data_ok: DWFO, path: ResolvedPath<'sg, LABEL, DATA>) -> Self;
 
     /// Maps the current container to a new one, based a provided mapping of the underlying environment.
     fn flat_map(
@@ -21,20 +20,20 @@ pub trait EnvContainer<'sg, 'rslv, LABEL: 'sg, DATA: 'sg, DWFO>:
     ) -> Self;
 }
 
-impl<'sg: 'rslv, 'rslv, LABEL, DATA> EnvContainer<'sg, 'rslv, LABEL, DATA, bool>
+impl<'sg: 'rslv, 'rslv, LABEL: Eq, DATA: Eq> EnvContainer<'sg, 'rslv, LABEL, DATA, bool>
     for Env<'sg, LABEL, DATA>
 where
-    ResolvedPath<'sg, LABEL, DATA>: Hash,
+    ResolvedPath<'sg, LABEL, DATA>: Hash + Clone,
 {
     fn empty() -> Self {
         Self::new()
     }
 
-    fn inject_if(data_ok: bool, path: ResolvedPath<LABEL, DATA>) -> Self {
+    fn inject_if(data_ok: bool, path: ResolvedPath<'sg, LABEL, DATA>) -> Self {
         if data_ok {
             return Env::single(path).into();
         } else {
-            return empty();
+            return Env::empty();
         }
     }
 
@@ -46,20 +45,22 @@ where
     }
 }
 
-impl<'sg: 'rslv, 'rslv, LABEL: 'sg, DATA: 'sg> EnvContainer<'sg, 'rslv, LABEL, DATA, bool>
+impl<'sg: 'rslv, 'rslv, LABEL, DATA> EnvContainer<'sg, 'rslv, LABEL, DATA, bool>
     for Rc<Env<'sg, LABEL, DATA>>
 where
     ResolvedPath<'sg, LABEL, DATA>: Hash,
+    LABEL: 'sg + Eq + Clone,
+    DATA: 'sg + Eq,
 {
     fn empty() -> Self {
         Self::new(Env::empty())
     }
 
-    fn inject_if(data_ok: bool, path: ResolvedPath<LABEL, DATA>) -> Self {
+    fn inject_if(data_ok: bool, path: ResolvedPath<'sg, LABEL, DATA>) -> Self {
         if data_ok {
             return Env::single(path).into();
         } else {
-            return empty();
+            return Env::empty().into();
         }
     }
 
@@ -80,22 +81,22 @@ impl<'sg, LABEL: 'sg, DATA: 'sg, E> From<Env<'sg, LABEL, DATA>>
     }
 }
 
-impl<'sg: 'rslv, 'rslv, LABEL: 'sg, DATA: 'sg, E: 'rslv>
+impl<'sg: 'rslv, 'rslv, LABEL: 'sg + Eq, DATA: 'sg + Eq, E: 'rslv>
     EnvContainer<'sg, 'rslv, LABEL, DATA, Result<bool, E>> for Result<Env<'sg, LABEL, DATA>, E>
 where
-    ResolvedPath<'sg, LABEL, DATA>: Hash,
+    ResolvedPath<'sg, LABEL, DATA>: Hash + Clone,
     E: Clone,
 {
     fn empty() -> Self {
         Ok(Env::empty())
     }
 
-    fn inject_if(data_ok: Result<bool, E>, path: ResolvedPath<LABEL, DATA>) -> Self {
+    fn inject_if(data_ok: Result<bool, E>, path: ResolvedPath<'sg, LABEL, DATA>) -> Self {
         data_ok.map(|ok| {
             if ok {
                 return Env::single(path).into();
             } else {
-                return empty();
+                return Env::empty();
             }
         })
     }
@@ -108,25 +109,29 @@ where
     }
 }
 
-impl<'sg: 'rslv, 'rslv, LABEL: 'sg, DATA: 'sg>
+impl<'sg: 'rslv, 'rslv, LABEL: 'sg + Eq, DATA: 'sg + Eq>
     EnvContainer<'sg, 'rslv, LABEL, DATA, FutureWrapper<'rslv, bool>>
     for FutureWrapper<'rslv, Env<'sg, LABEL, DATA>>
 where
-    ResolvedPath<'sg, LABEL, DATA>: Hash,
+    ResolvedPath<'sg, LABEL, DATA>: Hash + Clone,
     LABEL: Clone,
 {
     fn empty() -> Self {
         FutureWrapper::new(std::future::ready(Env::empty()))
     }
 
-    fn inject_if(data_ok: FutureWrapper<'rslv, bool>, path: ResolvedPath<LABEL, DATA>) -> Self {
-        data_ok.map(|ok| {
+    fn inject_if(
+        data_ok: FutureWrapper<'rslv, bool>,
+        path: ResolvedPath<'sg, LABEL, DATA>,
+    ) -> Self {
+        return FutureWrapper::new(async move {
+            let ok = data_ok.await;
             if ok {
                 return Env::single(path).into();
             } else {
-                return empty();
+                return Env::empty();
             }
-        })
+        });
     }
 
     fn flat_map(
diff --git a/scopegraphs/src/resolve/lookup.rs b/scopegraphs/src/resolve/lookup.rs
index 56f5e24..e088b2c 100644
--- a/scopegraphs/src/resolve/lookup.rs
+++ b/scopegraphs/src/resolve/lookup.rs
@@ -21,7 +21,7 @@ use crate::resolve::{
 use crate::{Label, Scope, ScopeGraph};
 use scopegraphs_regular_expressions::RegexMatcher;
 
-impl<'sg: 'rslv, 'storage, 'rslv, LABEL, DATA, CMPL, PWF, DWF, DWFO, LO, DEq> Resolve<'sg, 'rslv>
+impl<'sg: 'rslv, 'storage, 'rslv, LABEL, DATA, CMPL, PWF, DWF, LO, DEq> Resolve<'sg, 'rslv>
     for Query<'storage, 'sg, 'rslv, LABEL, DATA, CMPL, PWF, DWF, LO, DEq>
 where
     'storage: 'sg,
@@ -36,9 +36,10 @@ where
         'rslv,
         LABEL,
         DATA,
-    >>::EnvContainer: EnvContainer<'sg, 'rslv, LABEL, DATA, DWFO> + Debug,
+    >>::EnvContainer:
+        EnvContainer<'sg, 'rslv, LABEL, DATA, <DWF as DataWellformedness<DATA>>::Output> + Debug,
     PWF: for<'a> RegexMatcher<&'a LABEL> + 'rslv,
-    DWF: DataWellformedness<DATA, DWFO> + 'rslv,
+    DWF: DataWellformedness<DATA> + 'rslv,
 
     // DWF : DataWellFormedNess<DATA, Completeness::DWF>
     LO: LabelOrder<LABEL> + 'rslv,
@@ -105,7 +106,7 @@ type EnvC<'sg, 'rslv, CMPL, LABEL, DATA> = <<<CMPL as Completeness<LABEL, DATA>>
 
 type EnvCache<LABEL, ENVC> = RefCell<HashMap<EdgeOrData<LABEL>, Rc<ENVC>>>;
 
-impl<'storage, 'sg: 'rslv, 'rslv, LABEL, DATA, CMPL, DWF, LO, DEq, DWFO>
+impl<'storage, 'sg: 'rslv, 'rslv, LABEL, DATA, CMPL, DWF, LO, DEq>
     ResolutionContext<'storage, 'sg, 'rslv, LABEL, DATA, CMPL, DWF, LO, DEq>
 where
     LABEL: Label + Debug + Hash,
@@ -120,9 +121,10 @@ where
         'rslv,
         LABEL,
         DATA,
-    >>::EnvContainer: EnvContainer<'sg, 'rslv, LABEL, DATA, DWFO> + Debug,
+    >>::EnvContainer:
+        EnvContainer<'sg, 'rslv, LABEL, DATA, <DWF as DataWellformedness<DATA>>::Output> + Debug,
     DEq: DataEquivalence<DATA>,
-    DWF: DataWellformedness<DATA, DWFO>,
+    DWF: DataWellformedness<DATA>,
     LO: LabelOrder<LABEL>,
     Path<LABEL>: Clone,
 {
@@ -308,8 +310,13 @@ where
         let path = path.clone().resolve(data);
         let data_ok = self.data_wellformedness.data_wf(data);
 
-        return <EnvC<'sg, 'rslv, CMPL, LABEL, DATA> as EnvContainer<'sg, 'rslv, LABEL, DATA>>
-            ::inject_if(data_ok, path);
+        return <EnvC<'sg, 'rslv, CMPL, LABEL, DATA> as EnvContainer<
+            'sg,
+            'rslv,
+            LABEL,
+            DATA,
+            <DWF as DataWellformedness<DATA>>::Output,
+        >>::inject_if(data_ok, path);
     }
 
     /// Computes the edges in `edges` for which no 'greater' edge exists.
@@ -339,6 +346,16 @@ where
         log::info!("smaller({:?}, {:?}) = {:?}", edge, edges, smaller);
         smaller
     }
+
+    fn empty_env_container() -> EnvC<'sg, 'rslv, CMPL, LABEL, DATA> {
+        <EnvC<'sg, 'rslv, CMPL, LABEL, DATA> as EnvContainer<
+            'sg,
+            'rslv,
+            LABEL,
+            DATA,
+            <DWF as DataWellformedness<DATA>>::Output,
+        >>::empty()
+    }
 }
 
 #[cfg(test)]
@@ -348,6 +365,7 @@ mod tests {
     use crate::{
         add_scope,
         completeness::{ExplicitClose, FutureCompleteness, ImplicitClose, UncheckedCompleteness},
+        future_wrapper::FutureWrapper,
         query_regex,
         resolve::{DataWellformedness, Resolve, ResolvedPath},
         storage::Storage,
@@ -386,8 +404,11 @@ mod tests {
             }
         }
 
-        fn matcher(n: &'a str) -> impl DataWellformedness<Self, bool> {
-            |data: &Self| data.matches(n)
+        fn matcher(n: &'a str) -> impl DataWellformedness<Self> {
+            |data: &Self| {
+                let matches = data.matches(n);
+                return FutureWrapper::new(async move { return matches });
+            }
         }
 
         fn from_default(name: &'a str) -> Self {
diff --git a/scopegraphs/src/resolve/mod.rs b/scopegraphs/src/resolve/mod.rs
index d533595..3cc1d65 100644
--- a/scopegraphs/src/resolve/mod.rs
+++ b/scopegraphs/src/resolve/mod.rs
@@ -518,7 +518,7 @@ impl<'sg, 'storage, 'rslv, LABEL: Label, DATA, CMPL, PWF, DWF, LO, DEq>
         new_data_wellformedness: NDWF,
     ) -> Query<'sg, 'storage, 'rslv, LABEL, DATA, CMPL, PWF, NDWF, LO, DEq>
     where
-        NDWF: DataWellformedness<DATA, DWFO> + 'rslv,
+        NDWF: DataWellformedness<DATA> + 'rslv,
     {
         Query {
             _phantom: PhantomData,
diff --git a/scopegraphs/src/resolve/params.rs b/scopegraphs/src/resolve/params.rs
index 9efaed6..0d76d93 100644
--- a/scopegraphs/src/resolve/params.rs
+++ b/scopegraphs/src/resolve/params.rs
@@ -8,28 +8,31 @@ use crate::resolve::EdgeOrData;
 /// When executing the query, needs to be compatible with
 /// the completeness strategy for the underlying scope graph.
 ///
-pub trait DataWellformedness<DATA, O> {
+pub trait DataWellformedness<DATA> {
+    type Output;
     /// returns true if the data is well-formed.
-    fn data_wf(&self, data: &DATA) -> O;
+    fn data_wf(&self, data: &DATA) -> Self::Output;
 }
 
-impl<DATA, T, O> DataWellformedness<DATA, O> for T
+impl<DATA, T, O> DataWellformedness<DATA> for T
 where
     for<'sg> T: Fn(&'sg DATA) -> O,
 {
+    type Output = O;
+
     fn data_wf(&self, data: &DATA) -> O {
         self(data)
     }
 }
 
-/// When you don't specify the data well-formedness, this is the default.
-/// It considers all data well-formed.
 #[derive(Default)]
 pub struct DefaultDataWellformedness {}
 
-impl<DATA, O: From<bool>> DataWellformedness<DATA, O> for DefaultDataWellformedness {
-    fn data_wf(&self, _data: &DATA) -> O {
-        From::from(true) // match all data by default
+impl<DATA> DataWellformedness<DATA> for DefaultDataWellformedness {
+    type Output = bool;
+
+    fn data_wf(&self, _data: &DATA) -> bool {
+        true // match all data by default
     }
 }