W3C home > Mailing lists > Public > semantic-web@w3.org > December 2005

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

From: Adrian Walker <adrianw@snet.net>
Date: Thu, 08 Dec 2005 09:16:06 -0500
Message-Id: <5.0.2.1.2.20051208085126.02b8a6e0@pop.snet.net>
To: Danny Ayers <danny.ayers@gmail.com>
Cc: semantic-web@w3.org

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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Received on Thursday, 8 December 2005 14:16:30 GMT

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