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From: Jeremy Carroll <jjc@hpl.hp.com>
Date: Fri, 29 Feb 2008 15:45:36 +0000
Message-ID: <47C828A0.60601@hpl.hp.com>
To: "Web Ontology Language ((OWL)) Working Group WG" <public-owl-wg@w3.org>
CC: "Seaborne, Andy" <andy.seaborne@hp.com>

A further query I have had from colleagues concerns the relationship 
with the semantics of SPARQL queries.


talks about pattern matching, and blank nodes, complete with a link into 
RDF Semantics, which appears to be pertinent.

This allows a blank node in a basic graph pattern to match a named node 
or a blank node in the rdf graph being matched.

Boris at one point called the skolem semantics as 'SPARQL based' or 
something like that, and I am having increasing need for clarification 
as to quite what this means.

To what extent would this change impact compatibility between OWL DL and 
SPARQL, as we migrate from OWL 1.0 to OWL 1.1?

To make this concrete, here is a test case

SELECT  ?name
FROM    <http://example.org/A>
WHERE   { _:x eg:dp ?name }

where A is as before
_:a rdf:type owl:Thing.
eg:dp rdf:type owl:DatatypeProperty .
_:a eg:dp "foo".

If we read A with an RDF tool the answer is { ?name="foo" }.
If we read A with an OWL 1.0 DL toolset the answer is that {?name="foo"}
(I am not completely clear how we use SPARQL above OWL DL - is this an 
intended point of compatibility?)
If we read A with an OWL 1.1 DL toolset with the proposed resolution to 
ISSUE-3, then the answer is the empty set.

I am unclear as to what interop is expected between OWL DL and SPARQL, 
so maybe this example is unfair. However, clarification of this would be 

a) what interoperability is expected between OWL DL and SPARQL
b) what changes between 1.0 and 1.1

Received on Friday, 29 February 2008 15:46:34 UTC

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