Re: [w3ctag/design-reviews] WG New Spec: RDF 1.2 Concepts and Abstract Data Model (Issue #1159)

csarven left a comment (w3ctag/design-reviews#1159)

The TAG thanks the RDF & SPARQL WG for requesting this review and for the detailed discussion of versioning and compatibility considerations in RDF 1.2.

The TAG recommends the following:

Minor, on background and new work:

https://www.w3.org/TR/rdf12-primer/ references https://w3c.github.io/rdf-new/spec/ however it seems to be WIP with respect to changes between RDF 1.1 and 1.2. Noting https://www.w3.org/TR/rdf12-concepts/#changes-12  has information so suggest highlighting some of those (class 3+) in rdf12-primer.

https://www.w3.org/2021/12/rdf-star.html#background-and-motivation doesn't particularly explain "the problems that end-users were facing" (noting also "RDF's "end-users" are developers and information architect").

On version announcement:

[RFC 6838](https://datatracker.ietf.org/doc/html/rfc6838) explicitly states that new parameters should not introduce new functionality but may indicate metadata like a revision level. RDF 1.1 implementations will attempt to parse RDF 1.2 content as RDF 1.1 content, irrespective of any version announcement (media type parameter or in content). Since RDF 1.1 does not define behaviour for invalid or unknown syntax, and leaves error handling to implementations, there is the possibility of implementations behaving unpredictably or producing unsafe or incorrect results. RDF 1.2's version signalling is advisory: it helps compliant tools but cannot prevent RDF 1.1 parsers from attempting to process RDF 1.2 content.

RDF 1.1 parsers encountering RDF 1.2 content does not introduce a new problem category, since they have always faced unrecognised syntax, but the greater availability of RDF 1.2 content may increase how often this occurs in practice. These risks and the expectations for safe failure should be clearly documented so that the behaviour of implementations encountering unknown or incompatible RDF content is well understood. Consolidate and clarify the [RDF Version Announcement](https://www.w3.org/TR/rdf12-concepts/#section-version-announcement) guidance across the specs as well as work on [RDF 1.2 Interoperability](https://w3c.github.io/rdf-interop/SNAPSHOTS/DNOTE-rdf12-interop-20251216/Overview.html), ensuring consistent interpretation, including cases where no version parameter is provided.

Defining a new media type would clearly separate RDF 1.1 and 1.2 content. RDF 1.1 parsers would not process 1.2 content accidentally, preventing misinterpretation of new constructs. While more disruptive to implement, it avoids ambiguity and incorrect assumptions about content structure.

This review reflects the TAG's current assessment and is intended to support the Working Group's next steps. We are happy to discuss further if clarification is needed.

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