Fix the description of the record field annotation for link validation

[tom-tan]

The spec says:

If the value of jsonldPredicate is an object, and that object contains the field _type with the value @id, the field is a link field subject to link validation.

However, it is not correct because identity: false (or unspecified identity) is also needed as described in the section of JsonldPredicate#_type.

This request fixes it by clarifying the value of identity in addition to the field _type.

[tom-tan]

Uh...

Let me clarify the specification.

Which is correct?

• A field is the link field iff it has the jsonldPredicate field with _type: @id and identity: false (this request clarifies this case)
• A field is the link field iff it has the jsonldPredicate field with _type: @id, but its resolution rule is controlled with the value of identity

If the latter is correct, I will fix this request to mention the identity field.

[tetron]

A field is the link field iff it has the jsonldPredicate field with _type: @id, but its resolution rule is controlled with the value of identity.

If the latter is correct, I will fix this request to mention the identity field.

Identity controls which resolution rule to use. But also, identity: true means that it is not a reference, it is original object identifier, so the runtime should not do link validation to check that the identifier exists somewhere else. So link validation should be done on fields with either "identity: false" or identity is not specified.

Another way of specifying that a field is an identifier is with _id: @id.

It is inherited from JSON-LD where @id is used in various places in the context to mean something is a URI.

I can't recall exactly why I made a separate identity field, I imagine I needed finer grained control over the behavior for some special field but I do not remember the specific example. I'd have to dig into the git history.

[tetron]

Ok, I refreshed my memory.

There are fields that are identifiers. They identify the object they are found on.

However there are also fields whose values have the "identity" property. These are expanded like identifiers, but they don't identify the object they are found on, they just exist as a standalone value. The main example of this are the symbols of an enumeration.

[mr-c]

Ok, I refreshed my memory.

There are fields that are identifiers. They identify the object they are found on.

However there are also fields whose values have the "identity" property. These are expanded like identifiers, but they don't identify the object they are found on, they just exist as a standalone value. The main example of this are the symbols of an enumeration.

Thanks @tetron ; do we need to change/clarify the text still?

[codecov]

Codecov Report

Merging #631 (93ba1c6) into main (e0113b5) will not change coverage.
The diff coverage is n/a.

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