Re: Atomic reification

> On 25. Jan 2024, at 18:16, Andy Seaborne <andy@apache.org> wrote:
> 
> Points discussed about N-triples in the last two meetings e.g. [1], [2] meant I understood "atomic reification" differently.
> 
> https://github.com/afs/rdf-star-notes/blob/main/reif-atoms.md
> 
> "well-formed" gives some grouping but that is lost in N-triples. The test for it is expensive [3].
> 
> 
> To flesh out the problems with RDF 1.1 reification:
> 
> 1. Visually verbose (Turtle).
> 2. Verbose number of triples (N-Triples).
> 3. The reification triples may be spread across parts of a document.
>   This breaks visual proximity as written.
> 4. Over-specificed reifications (e.g. multiple rdf:subject)
> 5. Under-specificed reifications (e.g. no rdf:subject)
> 6. Presence or absence of rdf:Statement is unclear leading to
>   different SPARQL results. (De facto, it is omitted.)
> 7. If a large graph is split into multiple files of manageable size,
>   the triples can be split across those files (and blank nodes for
>   reification are broken).

As already mentioned yesterday in a mail [4] to this list I’m not so convinced by this  list. To cite [4]:

You give a list of 7 problems with RDF reification. Some of them (problems 4, 5 and 6) would be handled by a notion of wellformedness. Problem 1 would be solved by the proposed annotation syntax. Problems 3 and 7, especially blank nodes split over multiple graphs when breaking a big graph into files of a more manageable size, are not specific to reification but a general problem.
That leaves problem 2, verbosity in N-Triples, and that just comes with the terrain. There sometimes are more or less verbose ways to represent a complex type in straight triples - RDF Collections are much worse than RDF Containers - but RDF standard reification is not too bad in that respect.
You mention a reification atom <<(s p o)>> as a possible addition to N-Triples. That seems like a slight variation of N-Triples-Star to me, and I’m not fundamentally opposed if it helps and doesn’t rely on a new term type. My question is: does it really help? And would you also add list atoms, CBD atoms, graph atoms?

We discussed this already in follow-up mails [5] and [6].

In a further mail [7] I questioned the relevance of the problem 2 in streaming contexts.


Best,
Thomas


[4] https://lists.w3.org/Archives/Public/public-rdf-star-wg/2024Jan/0159.html
[5] https://lists.w3.org/Archives/Public/public-rdf-star-wg/2024Jan/0160.html
[6] https://lists.w3.org/Archives/Public/public-rdf-star-wg/2024Jan/0161.html
[7] https://lists.w3.org/Archives/Public/public-rdf-star-wg/2024Jan/0163.html

> The agreed Turtle syntax hides some of these issues (it addresses 1, it tends away from 4 and 5). It does not apply for N-triples, and not for SPARQL results when thought of as querying a triple table.
> 
> 
> The general idea, and as mentioned last week, is to introduce a unit "reification atom" that means the equivalents of rdf:subject/rdf:predicate/rdf:object are not split.
> 
> The agreed Turtle syntax applies.
> 
> 
> There has been requests for formal semantics in proposals so I have tried to provide that - I hope people here can help improve it in both presentation and content.
> 
> https://github.com/afs/rdf-star-notes/blob/main/reif-atoms.md
> 
> https://github.com/afs/rdf-star-notes/blob/main/reif-atoms-interpret.md
> 
>    Andy
> 
> [1] https://www.w3.org/2024/01/18-rdf-star-minutes.html#x123
> [2] https://www.w3.org/2024/01/19-rdf-star-minutes.html#x169
> [3] https://lists.w3.org/Archives/Public/public-rdf-star-wg/2024Jan/0136.html
>

Received on Friday, 26 January 2024 10:38:57 UTC