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RE: MT for imports (was: Re: Imports Proposal)

From: Smith, Michael K <michael.smith@eds.com>
Date: Wed, 13 Nov 2002 10:22:52 -0600
Message-ID: <B8E84F4D9F65D411803500508BE3221411D8ECB9@USPLM207>
To: Jim Hendler <hendler@cs.umd.edu>, pat hayes <phayes@ai.uwf.edu>, Jeff Heflin <heflin@cse.lehigh.edu>
Cc: www-webont-wg@w3.org

>If the WG decides to go with one of these import closures things (and 
>Pat's examples below show yet more reasons I worry if we've got it 
>right) we need to make sure we handle cycles in some correct way.

Which is why all of the serious proposals compute the transitive closure
of imports.

Re Pat's questions.  I think they are not at this time our concern.
I thought we had explicitly rejected dealing with things like webs of
trust.  Neither should WE be worrying about issues of cache coherency.
Someone will have to, just not us. 

This is another reason why I prefered not getting entailment involved 
in the details of imports.  As Pat's examples point out yet again, 
imports keeps bumping into these fundamentally operational issues.

In order to address the problems that Pat raises, I suspect (guessing)
that the distributed ontologies that work will use naming conventions
to create versions.  That is, wine.owl will start out linked to
wine_v_1.owl.
As the wine ontology evolves, wine.owl will be linked to the successive 
versions.  If I am extending wine.owl and am concerned about change 
to the underlying ontology, I will import wine_v_1.owl, not wine.owl.

What we want to provide is some minimalist scaffolding that can be used
for initial experiments in how to build distributed knowledge bases.

- Mike

Michael K. Smith, Ph.D., P.E.
EDS - Austin Innovation Centre
98 San Jacinto, #500
Austin, TX  78701

* phone: +01-512-404-6683
* mailto:michael.smith@eds.com



-----Original Message-----
From: Jim Hendler [mailto:hendler@cs.umd.edu]
Sent: Wednesday, November 13, 2002 8:57 AM
To: pat hayes; Jeff Heflin
Cc: www-webont-wg@w3.org
Subject: Re: MT for imports (was: Re: Imports Proposal)



Here's another one for you guys - really happened - I have two 
students who wanted their ontologies linked -  no changes involved 
but:
   A publishes P importing Q
   B publishes Q importing P
If the WG decides to go with one of these import closures things (and 
Pat's examples below show yet more reasons I worry if we've got it 
right) we need to make sure we handle cycles in some correct way.
  -JH





At 9:46 AM -0500 11/13/02, pat hayes wrote:
>Jeff, your email got me thinking about the intricacies which arise 
>when thinking about imports in the context of a changing world. Here 
>are few more example scenarios. In each case A, B, C etc are people, 
>P, Q, R, etc are chunks of OWL in documents. 'changes' means 
>altering the RDF at a given URL.
>
>1.
>A publishes P
>B publishes Q importing P
>A changes P (to P')
>C reads Q and imports P'
>
>Now, has C got it right, or not? Or should C have imported P (how?) 
>Or should B have tracked A's changes (how?)
>
>2.
>A publishes P
>B publishes Q
>C publishes R importing Q
>B changes Q to Q' importing P
>D reads R
>
>Has D got it right? This is really a special case of the first one, 
>but since the change involves an imports, the effect is magnified, 
>as it were. Obviously, the change could be arbitrarily far along an 
>imports-reference chain.
>
>3.
>A publishes P
>B publishes Q importing P
>A's server crashes
>C reads Q , concludes that the imports P is empty, archives the result
>A's server comes back online
>
>Now has C got it right? Or should C have refused to archive an 
>empty-due-to-404  imports statement?
>
>Pat
>
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-- 
Professor James Hendler				  hendler@cs.umd.edu
Director, Semantic Web and Agent Technologies	  301-405-2696
Maryland Information and Network Dynamics Lab.	  301-405-6707 (Fax)
Univ of Maryland, College Park, MD 20742	  240-731-3822 (Cell)
http://www.cs.umd.edu/users/hendler
Received on Wednesday, 13 November 2002 11:23:15 GMT

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