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Re: comments on SPARQL Query Language for RDF

From: Simon Schenk <sschenk@uni-koblenz.de>
Date: Tue, 19 Jun 2007 17:18:17 +0200
To: Lee Feigenbaum <feigenbl@us.ibm.com>
Cc: public-rdf-dawg-comments@w3.org
Message-Id: <1182266297.6046.22.camel@lapace01>

Hi everybody,

you may be interested in our Datalog based SPARQL semantics proposed in
[1]. The paper has been accepted for the German AI conference in
September.

We propose a mapping of more or less all of SPARQL into datalog
programs, including UNION, OPTIONAL and BOUND. As has been pointed out
here, this is not always straight forward, but possible. The semantics
of a SPARQL query is then defined using a query against the datalog
program.

Please note that this work is s couple of months old and I have not yet
checked, whether it conforms to the latest version of the spec.

There is other work in this direction by Polleres. Additionally I assume
that for example KAON2 does a similar mapping.

Best regards,
Simon

[1]
http://www.uni-koblenz.de/~sschenk/publications/2007/KI2007SparqlSemantics.pdf



Am Dienstag, den 05.06.2007, 14:12 -0400 schrieb Lee Feigenbaum:
> Hi Bob,
> 
> Bob MacGregor <bmacgregor@siderean.com> wrote on 06/04/2007 09:49:45 PM:
> 
> > Hello Lee,
> > 
> > On Jun 4, 2007, at 1300, Lee Feigenbaum wrote:
> > 
> > Bob MacGregor wrote on 05/31/2007 07:52:26 PM:
> > 
> > My argument is against the choice of an algebraic semantics instead 
> > of a declarative
> > semantics.  Unless I am mistaken, OWL has a declarative semantics, and I
> > would assume that SWIRL and RuleML have or will each have a 
> > declarative semantics.
> > Suppose X would like to implement rules from one of these languages 
> using
> > SPARQL to evaluate the rule bodies.  If the semantics of SPARQL aligns 
> with
> > the rule language, or perhaps with a subset of it, then X can 
> comfortably use
> > SPARQL for this task.  However, comparing a declarative (rule) 
> > semantics with an
> > algebraic (SPARQL) semantics is an apples and oranges comparison.  To be
> > sure that SPARQL properly implements the rules, X would have to produce 
> > the declarative semantics on her own.
> > 
> > A declarative semantics forms a bedrock on which to build a logic
> > pyramid.  An algebraic semantics is essentially a dead-end.
> 
> Thanks for your comments. We're recording your feedback as a formal 
> objection. To help us properly record and represent the objection, please 
> let me know if there are any example queries that illustrate a difference 
> in the declarative semantics you are looking for compared to the current 
> semantics in the document.
> 
> > I wasn't recommending eliminating UNBOUND from the language; I was 
> > recommending 
> > relegating it to secondary status within the language, i.e., making it 
> > a computed predicate and not according it a reserved word.  Its easily 
> the
> > most egregious hack in the language.
> 
> We'll also note this objection. I'm unclear as to whether you are 
> objecting to the existence of the bound operator altogether, or to the 
> potential combination of the bound operator and the logical-not operator. 
> If you could clarify this, it would help me best represent your objection 
> as the WG seeks advancement along the Rec. track.
> 
> many thanks,
> Lee
> 
> > 
> > thanks,
> > Lee
> > 
> > Cheers, Bob
> > 
> > Bob MacGregor
> > Chief Scientist
> > Siderean Software, Inc.
> > 310.647.5690
> > bmacgregor@siderean.com
Received on Tuesday, 19 June 2007 15:18:46 GMT

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