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Re: RIF/SPARQL Semantics (Was -- Rule usage description...)

From: Lee Feigenbaum <lee@thefigtrees.net>
Date: Sun, 12 Dec 2010 10:49:10 -0500
Message-ID: <4D04EEF6.7020402@thefigtrees.net>
To: Adrian Walker <adriandwalker@gmail.com>
CC: Semantic Web <semantic-web@w3.org>
On 12/12/2010 9:23 AM, Adrian Walker wrote:
> Hi Ivan & All --
>
> There would seem to be an opportunity here to move the W3C approach to
> rules and SPARQL onto a firmer semantic base.

Hi Adrian,

Please send any comments on the SPARQL 1.1 documents to 
public-rdf-dawg-comments@w3.org.

> The basic idea is to define what answers a rule system or SPARQL should
> give to /any /question, based on /any /set of triples, using a logical
> model theory.  The theory then works as a "gold standard" for
> implementers.  W3C could provide test suites.

The SPARQL Query Language is defined in terms of algebraic semantics, 
rather than a model theoretic semantics. The original Data Access 
Working Group did consider this suggestion and decided to remain with 
the existing approach, in addition to the test suite. The current SPARQL 
Working Group also intends to publish a test suite to aid 
interoperability in implementations of SPARQL 1.1.

best,
Lee

> Looking backwards for a moment, SQL suffers from  the lack of such a
> base or standard.  There is a query which produces different answers
> over the same data in two of the leading  SQL implementations (and both
> answers are intuitively wrong).  That's not fatal for SQL, since one can
> 'program around it', but a similar flaw is extremely serious for
> RIF/SPARQL, since it's supposed to work the same everywhere on the Web.
> How would we ever trust the answers?
>
> An early version a model theoretic standard is in [1,2].   There's an
> illustration of how it can work in practice with RDF in [3,4].
>
> Hope this helps.
>
>                                       -- Adrian
>
> [1]  Towards a Theory of Declarative Knowledge, (with K. Apt and H.
> Blair). In: Foundations of Deductive Databases and Logic Programming, J.
> Minker (Ed.), Morgan Kaufman 1988.
> http://oai.cwi.nl/oai/asset/10404/10404A.pdf
>
> [2]  Backchain Iteration: Towards a Practical Inference Method that is
> Simple   Enough to be Proved Terminating, Sound and Complete. Journal of
> Automated Reasoning, 11:1-22
>
> [3] www.w3.org/2004/12/rules-ws/paper/19
> <http://www.w3.org/2004/12/rules-ws/paper/19>
>
> [4] www.reengineeringllc.com/demo_agents/RDFQueryLangComparison1.agent
> <http://www.reengineeringllc.com/demo_agents/RDFQueryLangComparison1.agent>
Received on Sunday, 12 December 2010 15:49:49 GMT

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