AW: proposal: a reifier should reify only one "thing"

About
„
I'm more and more convinced that a reifier should not reify several things
„

And

„
* it is not enforced syntactically (the following is valid RDF: :t rdf:object :s1, :s2. ),
* it is not enforced semantically (the example above does not entail :s1 owl:sameAs :s2 ).
“

What RFC2119 language would you then use for the “should” in your statement?

Best,

Felix

Von: Pierre-Antoine Champin <pierre-antoine@w3.org>
Datum: Donnerstag, 18. April 2024 um 01:18
An: RDF-star WG <public-rdf-star-wg@w3.org>
Betreff: proposal: a reifier should reify only one "thing"

Hi all,

after writing my response to Phil [1], which is a refinement of the arguments I made last Friday [2], I'm more and more convinced that a reifier should not reify several things, because it would lead to wrong expectations ("this is similar to a named graph, right?") and counter-intuitive inferences (again, see my example in [1]).

That being said, I would have this constraint only expressed  the "intended meaning" of the rdf:reifies predicate -- in a way very similar to rdf:subject, rdf:predicate and rdf:object. Reading the description of these predicate in [3] strongly hints at the fact that they are supposed to have only one value each ("[rdf:subject] is used to state the subject of a statement"), but

* it is not enforced syntactically (the following is valid RDF: :t rdf:object :s1, :s2. ),
* it is not enforced semantically (the example above does not entail :s1 owl:sameAs :s2 ).

The arguments against such an enforcement (syntactic or semantic) have been largely discussed already, I won't repeat them here.



Finally, I want to emphasize that, although I advocate that a reifier should reify only one thing, I would like to remain very vague on what kind of "thing" that is, and how many (syntactically) distinct triples would actually identity that thing.

For example, from the following graph

    :r rdf:reifies
        <<( dbr:Linköping dbo:populationTotal 104232 )>>.

it would seem appropriate to infer (under D-entailment where xsd:integer ∈ D)

    :r rdf:reifies
        <<( dbr:Linköping dbo:populationTotal 104232 )>>,
        <<( dbr:Linköping dbo:populationTotal 00104232 )>>.

(I believe that it would be the case with the semantics currently proposed by Enrico).

From the following graph

    :r rdf:reifies
        <<( :alice :knows :bob )>>.
    :knows a owl:SymetricProperty.

MAYBE it would be appropriate to infer

    :r rdf:reifies
        <<( :alice :knows :bob )>>,
        <<( :bob :knows :alice )>>.

From the following graph

    :r rdf:reifies
        <<( :alice :worksWith :bob )>>.
    :worksWith rdfs:subPropertyOf :knows.

MAYBE it would be appropriate to infer

    :r rdf:reifies
        <<( :alice :worksWith :bob )>>,
        <<( :alice :knows :bob )>>.

I don't have a definite answer for the two examples above, and I don't think that we need to answer them urgently. I'm just pointing out that we have some leeway even if we settle on "a reifier reifies only one thing".

  pa
[1] https://www.w3.org/mid/d39fcb64-66d6-4cbe-9453-a52d1cbd5259@w3.org

[2] https://www.w3.org/2024/04/12-rdf-star-minutes.html#x169

[3] https://www.w3.org/TR/rdf11-schema/#h3_ch_reificationvocab