- From: Thomas Lörtsch <tl@rat.io>
- Date: Thu, 8 Aug 2024 13:37:26 +0200
- To: Andy Seaborne <andy@apache.org>
- Cc: public-rdf-star-wg@w3.org
> On 6. Aug 2024, at 16:16, Andy Seaborne <andy@apache.org> wrote: > > > > On 05/08/2024 16:37, Thomas Lörtsch wrote: > > some help from SPARQL. > > If it is RDFS-star entailment regime, there is nothing extra to do in SPARQL. Yes, if … but in general we can’t rely on RDFS entailment to be available to us. > >> SPARQL >> ====== >> In Friday’s meeting we discussed if SPARQL should support stated triple terms by querying for them too, even when the BGP only mentions reified triple terms. To that end 'rdfs:states' should be defined as a subproperty of rdf:reifies. >> However, upon further reflection it seems to me that the real benefit > > The WG has been using use cases. It would be helpful to have a use case to justify a feature - is it common enough to motivate special syntax given it can already be done in RDFS-star. See my extra mail on that [0] >> would be in having any query search not only all (standard) triples but also all stated triple terms. E.g. a query for >> ?s ?p ?o >> over the following graph >> _:t1 rdfs:states <<( :s :p :o )>> ; >> :a :b. >> _:t2 rdfs:reifies <<( :x :y :z )>> ; >> :c :d. >> would return also the triple from the stated triple term, but not from the reified one: >> _:t1 rdfs:states <<( :s :p :o )>> . >> _:t1 a :b . >> :s :p :o . >> _:t2 rdfs:reifies <<( :x :y :z )>>. >> _:t2 :c :d. >> This might be made the standard behaviour of SPARQL-star or a switchable configuration option or a keyword (something like "WITH STATED"). > > Breaking the relationship of pattern matching and simple entailment is a major step. Why this feature and not others? Because we are only working on RDF-star, not other issues, and because it might help very much in ironing out the kinks in RDF-star. At least that’s the idea. > No configuration options. A query should give the same answers at all endpoints with the same data. > > With simple entailment, the user writes: > > SELECT ?r { > ?r rdf:states|rdf:reifies ?T . > } > > and for statements and stated terms (mentioned else thread) > > SELECT ?r { > ?r rdf:states <<( ?s ?p ?o )>> . > } > > Property paths break up BGPs. Not sure why you mention property paths here - maybe I’m missing something. But since you mention it, I was about to ask the following anyway: why is using property paths on triples in annotation syntax not allowed (see Example 14 in the CG report [1])? > From a data access point of view, multiple properties are a burden in query writing, it would be better to qualify the reifier: > > Data: > > :r rdf:reifies <<( :s :p :o )>> . > :r rdf:type rdf:Stated . > > then > > SELECT ?r { > ?r rdf:reifies ?T . > } > > finds all reifiers > > SELECT ?r { > ?r rdf:type rdf:Stated . > } > > finds stated ones > and > > SELECT ?r { > ?r rdf:type rdf:Description . > } > > finds describing reifiers. > > This is open - there can be other characteristics related to reifiers e.g source. We discussed this already: it solves the problem to some degree, but it adds considerably to the triple count. Would you want the canonical mapping from :s :p :o {| :a :b |} . to n-triples to be :s :p :o . _:r rdf:reifies <<( :s :p :o )>> . _:r rdf:type rdf:Stated . ? You were concerend about additional query complexity if a second property like rdf:states as a subproperty of rdf:reifies is introduced. How would the necessity to query for an extra typing triple compare to that? Thomas > Andy > [0] https://lists.w3.org/Archives/Public/public-rdf-star-wg/2024Aug/0032.html [1] https://w3c.github.io/rdf-star/cg-spec/2021-12-17.html#example-14 >
Received on Thursday, 8 August 2024 11:37:35 UTC