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Re: Formal Semantics of OWL + RDF + SPARQL + SWRL

From: Harry Halpin <hhalpin@ibiblio.org>
Date: Thu, 08 Dec 2005 14:25:20 +0000
Message-ID: <43984250.5040404@ibiblio.org>
To: semantic-web@w3.org

While I appreciate Adrian's demonstrations, I'm just going to point out
that while phrasing things in  natural language explanations will
clearly be useful for the semantic web, it doesn't correct - in fact it
makes worse - the questions of ambiguity that I think were trying to be
addressed by formal semantics to begin with.

I don't think we have any choice but to assume any triple-store is not
*just* the triple store but *the triple-store plus standardized
inferences.* With vanilla XML is what you see is what you get, but in
RDF that does not seem to hold all the time.

Adrian Walker wrote:

>
> Danny --
>
> You mentioned...
>
>> the issue of stores
>> containing identical data responding differently to the same query
>> (depending on their inference capability)
>
>
> As you know, many of the inference systems currently in use take a
> procedural approach -- e.g. forward chaining rule firing is
> commonplace.  Thus, the results from a query depend on which version
> of which method is being used.
>
> Up till now, inference systems have mainly been used standalone, so it
> has been just about possible to live with such a situation. 
> (Although, arguably, some major commercial inference-based projects
> have failed because of such a procedural approach.)
>
> However, it's hard to see how this could continue to "sort of work" in
> a (semantic) web context.  The situation is going to get very messy
> very fast, and no business person is going to trust results obtained
> from such a software mess.  E.g., a look at the jena-dev list almost
> any day yields "unexpected inference" questions.
>
> Two fixes come to mind.
>
> Fix 1:  Move all inferencing for the SW to *highly* declarative
> reasoners that are compliant to a formal model theory that *defines*
> what results must follow from *any* database-query pair, as in e.g. 
> [1] .  Provide English explanations of results, at the non-programmer,
> business level.
>
> Fix 2:   Note that Fix 1 would require many vendors to trash their
> products, and that is unrealistic in the short term.  Persuade W3C and
> other standards bodies to recommend an approach based on message
> passing between inference systems -- in which each message *must* be
> an English sentence that describes its meaning in the real world. 
> This approach is argued in more detail in [2].
>
>  How does that sound?   Thanks in advance for comments.
>
>                                 -- Adrian
>
> [1]  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.
>
> [2]  Understandability and Semantic Interoperability of Diverse Rules
> Systems
> www.w3.org/2004/12/rules-ws/paper/19
>
>
>
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>
> Adrian Walker
> Reengineering
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>
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Received on Thursday, 8 December 2005 14:25:42 GMT

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