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RDF(S) tests and semantics

From: Steve Harris <S.W.Harris@ecs.soton.ac.uk>
Date: Tue, 5 Aug 2003 22:53:27 +0100
To: www-rdf-interest@w3.org
Message-ID: <20030805215327.GA30743@ecs.soton.ac.uk>

Hi,

I've been running the RDF conformance tests against the current version of
3store and I have some observations:

According to
http://www.w3.org/2000/10/rdf-tests/rdfcore/rdfms-seq-representation/Manifest.rdf#test002 the empty document should entail:

<rdf:_1> <rdf:type> <rdfs:ContainerMembershipProperty> .

But Section 4.2/2 of the RDF Semantics document
(http://www.w3.org/TR/rdf-mt/) says:
"Add all triples of the following forms [rdf:_* rdf:type CMP]. This is an
infinite set because the RDF container vocabulary is infinite. However,
since none of these triples entail any of the others, it is only
necessary, in practice, to add the triples which use those container
properties which actually occur in any particular graph or set of graphs
in order to check the rdfs-entailment relation between those graphs."

The MT document's description seems more sensible to me as otherwise there
is no way to finitly resolve the query
(?foo, <rdf:type>, <rdfs:ContainerMembershipProperty)

I'm also concerned that its not possible to efficiently implement the new
Literal and Datatype entailments, and they do not seem to be optional.
Adding them would add another few million triples to our production KB and
seems to produce confusing entailments. What is the intended meaning if you
add
	<foo> <bar> "10"
which (I think) entails
	<foo> <bar> _:something                   (by
	_:something <rdf:type> <rdfs:Literal>      rdfD 1)

It seems to just produce unhelpful results if you query for
(<foo>, <bar>, ?o)

What is the scope of _:something, I gather its supposed to be the
same ID for all literals that are byte-for-byte identical and have the
same datatype, but what happens when you merge graphs with different
nodes for _:something? How do you associate a given literal with the
corresponging bNode? Is it incorect for two identical literals to have
different bNodes, or identical bNodes to have different literals and if
so, how do you avoid this?

- Steve

-- 
Stephen Harris                    07970 557047
AKT, IAM Research Group          023 8059 2831
University of Southampton, UK
swh@ecs.soton.ac.uk     http://www.aktors.org/           
Received on Tuesday, 5 August 2003 17:53:30 GMT

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