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Re: Thinking out lout about some strange SPARQL entailment test cases...

From: Birte Glimm <birte.glimm@comlab.ox.ac.uk>
Date: Fri, 27 Aug 2010 20:11:39 +0100
Message-ID: <AANLkTi=wSH2F0KN7msNEqU5DcUqEFJLndtUd9ASYTbGv@mail.gmail.com>
To: Axel Polleres <axel.polleres@deri.org>
Cc: SPARQL Working Group <public-rdf-dawg@w3.org>
Sorry, I didn't comment on the second test case

> Similarly:
>  G:
>   :s :p 1
>  Q:
>  WHERE { ?L a xsd:integer }

I think that would need datatype awareness and RDFS does not support
the XSD schema datatypes (you would need D-Entailment or higher). Even
if we have
:s :p "1"^^xsd:integer.
a system unaware of xsd datatypes might read that triples, but it will
not necessarily infer
"1"^^xsd:integer a xsd:integer .
or even
"1"^^xsd:integer a xsd:short .
which is also true I guess. At least for OWL reasoners what counts
internally is the denoted data value and "1"xsd:short and
"1"xsd:integer is the same data vale with different lexical forms. Now
for OWL Direct Semantics that BGP is not legal, so your only hope
would be OWL with RDF-Based Semantics or some D-Entailment

Now, even with XSD awareness and not counting it as illegal RDF, the
answers would not be infinite because you only consider the data
values in the graph.


> Obviously, those will not give an answer, but some people might expect those to return surrogate blank nodes... a colleague of mine just came to me with that (in a different context), and I thought I might share it.
> Axel

Dr. Birte Glimm, Room 309
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Received on Friday, 27 August 2010 19:12:07 UTC

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