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Re: LANG: syntactic version for imports (and other things)

From: Jeff Heflin <heflin@cse.lehigh.edu>
Date: Wed, 18 Sep 2002 17:43:11 -0400
Message-ID: <3D88F36F.253C3534@cse.lehigh.edu>
To: pat hayes <phayes@ai.uwf.edu>
CC: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>, www-webont-wg@w3.org

pat hayes wrote:
> 
> I agree with Peter, but how about the following suggestion for
> re-phrasing this in terms of entailment. If an ontology A contains
> [import B] (in whatever notation turns out to be appropriate) and if
> B + A entails C then A entails C, where '+' means whatever is the
> appropriate 'conjunction' (merging) operation on ontologies.  (For
> bare RDF that would be a triples-graph merge, but OWL might have a
> more sophisticated notion involving the addition of some extra stuff
> to keep the merge tidy; whatever. The point here is that we will need
> this notion to be defined for ANY web ontology language, so whatever
> it is, 'imports' refers to that.)

That's sounds fine to me, but I don't think its any different from my
original proposal which could be restated as "if ontology A contains
[import B] and B entails P then A entails P." Doesn't all the
entailments of B+A fall out that way? It's the end of the day and I'm
tired :-(

However, if you agree with Peter and I agree with this, maybe we've all
been in violent agreement all along?

> Now, one can take this to be a constraint on what 'entails' means, or
> one can take it instead to be a specification constraint on behaviors
> of reasoners: that in order to be complete with respect to
> entailment, a reasoner needs to somehow 'merge' the content of the
> imported ontology (and hence, the transitive closure of other
> imported ontologies that they might require in order to be complete).
> But there are many ways one might do that: by copying and caching B
> into A, by retrieval from B during inference from A when needed, if
> that is possible, or even by querying B using a query language (under
> some circumstances). But that decision - or indeed, the decision to
> completely ignore B - can be left to the implementation. An engine
> that makes no pretensions to completeness - and I hereby predict that
> almost all deployed reasoners will not make any such claims, since
> they will be largely meaningless in a real web context - can choose
> to ignore imports statements, or to treat them very casually, for
> example, and still conform to this kind of spec.

That's fine.

> I think any spec that *requires* imports to be implemented by a
> syntactic copy is simply not acceptable and will not be used; and
> that in any case it is not necessary.  And all such interpretations
> run foul of the syntactic vagaries of XML and RDF.

I agree whole-heartedly.

> 
> Pat
> 
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Received on Wednesday, 18 September 2002 17:43:16 GMT

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