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SPARQL 1.1 entailment regimes and query with FROM clause

I'm currently documenting/testing about SPARQL 1.1 entailment regimes and the recommendation repeatedly states that

The scoping graph is graph-equivalent to the active graph

but it does not specifies what is the active graph referring to : is it the data-set used in the query ? a union of all graphs in the store ?

As a test to determine this , I got this graph URIed <http://www.example.org/> in a Sesame Memory store with RDF Schema and direct type inferencing store (v2.7.14)

@prefix ex:<http://www.example.org/> .
ex:book1 rdf:type ex:Publication .
ex:book2 rdf:type ex:Article .
ex:Article rdfs:subClassOf ex:Publication .
ex:publishes rdfs:range ex:Publication .
ex:MITPress ex:publishes ex:book3 .

I've been trying the following query (which means using the default graph thus the inference engine) 

SELECT ?s WHERE { ?s a ex:Publication . }

As expected, it returns me all three instances

<http://www.example.org/book1>
<http://www.example.org/book2>
<http://www.example.org/book3>

while the query :

SELECT ?s FROM ex: WHERE { ?s a ex:Publication . }

returns only

<http://www.example.org/book1>

Under the said circumstances, shouldn't both results be the same?

What should happen (according to the recommendation) if data and schema are split between two graphs in the store (like <urn:rdfs-schema> and <urn:data>, or even scattered across more graphs) and the query uses both graphs (or a subset of schema-related graphs) in the FROM clause instead of the default graph ?

Meaning should the inferencing be global throughout the store or does it depend on the query dataset ?

Or maybe is the recommendation loose enough to make this an implementation dependent issue ?

Thanks for your lights,

Max.

EDIT this question is being redirected to SPARQL 1.1 entailment regimes and query with FROM clause (follow-up)

Solution

  • Your second query only returns only book1 because in Sesame's RDFS inferencer, entailed statements are inserted in the default graph, not in the named graph(s) from which the premises for the entailment come. So the entailed results are simply not present in the graph you are querying.

    The reason for this design choice is at least partly historic, as the Sesame RDFS inference engine predates the W3C notion of entailment regimes. The rationale at the time was that in the case of inferencing over several named graphs (where e.g. one premise comes from graph A and another from B), insertion in the default graph (rather than in either A, or B, or both) was simplest with the least amount for confusion.

    Sesame currently does not explicitly support the W3C entailment regimes specification. However, if you feel that a simple improvement would be possible to make it more compatible, by all means log a feature request.

    (disclosure: Sesame developer)