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

From: Adrian Walker <adriandwalker@gmail.com>
Date: Sun, 12 Dec 2010 12:01:09 -0500
Message-ID: <AANLkTimG7rcKB_MHeQwfKJ=6_rmZ-wE_sVK_YdhwQhDy@mail.gmail.com>
To: Lee Feigenbaum <lee@thefigtrees.net>
Cc: Semantic Web <semantic-web@w3.org>, public-rdf-dawg-comments@w3.org
Hi Lee,

You wrote...

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.

Where do things stand currently with the semantics of negation and
aggregation please?  (At one time, RIF/SPARQL negation was out of semantic
scope, but with several different hacks available -- a sure sign of future
trouble if not addressed with a spec)

                                  Thanks,  -- Adrian

Internet Business Logic
A Wiki and SOA Endpoint for Executable Open Vocabulary English Q/A over SQL
and RDF
Online at www.reengineeringllc.com
Shared use is free, and there are no advertisements

Adrian Walker
Reengineering


On Sun, Dec 12, 2010 at 10:49 AM, Lee Feigenbaum <lee@thefigtrees.net>wrote:

> 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 17:02:45 GMT

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