Modeshape Impl: Interaction models effectively can't be changed

[escowles]

Section 3.2.1 says that PATCH must not allow changing interaction models to non-subtypes. But my reading of the LDP ontology and the types that the Modeshape implementation supports (NonRDFSource, BasicContainer, DirectContainer, IndirectContainer) means that you effectively can't change the interaction model after creating a resource (because none of those types are subtypes of any of the other types).

In order to allow changing to a subtype, an implementation would need to allow creating Resource, RDFSource or Container types.

I don't think this is a problem, but I wanted to raise it as a non-obvious consequence of the spec and the choices made in the Modeshape implementation.

[birkland]

Re-reading this, it has the consequence of:

• If a repository advertises a Link rel=type of a "most specific" type, then it cannot be changed (i.e If a resources advertises the headerLink: <ldp:BasicContainer"; rel=type, that resource cannot be changed to DirectContainer, Container, etc).
• If a repository advertises a less-specific superclass in the link header (e.g. ldp:Container or ldp:Resource), then
  1. Absent a priori knowledge, a client needs to infer its most specific interaction model by inspecting the triples by looking for ldp:hasMemberRelation or ldp:isMemberOfRelation in order to know it is a direct container, or ldp:insertedContentRelation in order to know it is an indirect container.
  2. The most specific model can be changed (e.g BasicContainer to IndirectContainer) by modifying the resource's triples via PUT or PATCH

[awoods]

As a note, Cavendish creates RDFSources in the absence of a client-provided interaction model.