Re: Presentation about reifiers and graphs

Hi Niklas!

> On 14. Sep 2024, at 13:28, Niklas Lindström <lindstream@gmail.com> wrote:
> 
> Dear all,
> 
> I've drafted a presentation for the purpose of introducing reifiers
> and comparing them to graphs. It's currently at:
> https://niklasl.github.io/rdf-docs/presentations/RDF-reifiers-1/
> 
> Ora: you're of course free to take what you like and discard the rest
> for your TPAC slides.
> 
> I tried to keep it on par with the baseline, but of course there may
> be wording in there still to be agreed upon. If you see fit I can make
> a PR for further collaboration in getting a version of it to
> https://github.com/w3c/rdf-star-wg/tree/main/docs.
> 
> Best regards,
> Niklas
> 


About slide #9:

I think a good abstraction for this is "orthogonality":

- in "References (utterances, source provenance)" the annotation takes a very orthogonal perspective to what is stated. The annotation doesn’t refer to the topic of discourse but rather to some "external" aspect like some kind of administrative detail or application-specific context. It talks about the statement as an entity in its own right.

- in "Circumstances (qualifying events or situations)" the annotation is concerned with the topic of discourse itself, adding further detail to the description provided by the statement. It may even refer to the property or specific nodes. In that sense it is "aligned with" and "parallel to" what the annotated statement describes.

Of course there are not only those two extreme options but any kind of in-betweens.



About slide #15

- "The triples reified do form a potential subgraph of the graph in which the reifier is described."

Is that meant to say that the reified statementa are not necessarily asserted in the graph? If yes then the wording seems a bit involved to me and also I’d rather make it a topic of its own (and not discuss it as a graph-related topic). If not, then I don’t understand it.


- "But a reifier is not necessarily defined by the triple or triples it reifies. (Just as a thing is not necessarily defined as the set of things it relates to.)"

That is confusing me. How about this:
"The reifier refers to an entity in the realm of interpretation, and the entity is described by the triple term(s) so reified. The description is not necessarily complete."
Does this capture what you try to express? Or how does it differ in your opinion?



About slide #18:

How about an example that models a named graph with triple terms, like so:

```
_:ng rdfx:rdf11namedGraphOf <<( :s :p :o )>> , 
                            <<( :a :b :c )>> .
```

And then refer to the RDF 1.1: On Semantics of RDF Datasets note for all the possible semantics of `rdfx:namedGraphOf`.

This might be an interesting example w.r.t. to the discussion about well-formedness conditions. This `rdfx:rdf11namedGraphOf` can probably not be understood as a subproperty of `rdf:reifies` because RDF 1.1 named graphs have no defined relation between name and graph. So would we disallow it? Different discussion, t.b.c. elsewhere.



About slide #19:

This is slightly mined territory, as you are probably aware ;-) The Nested Named Graph proposal [0] - which was rejected by the WG without too much discussion - claims that it is possible to add those missing pieces without breaking existing applications. Named graphs can then be used to represent reifiers and vice versa. Caveat: SPARQL is another question.


Best,
Thomas



[0] https://github.com/rat10/nng

Received on Monday, 16 September 2024 13:05:25 UTC