W3C home > Mailing lists > Public > www-webont-wg@w3.org > November 2002

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

From: <dlm@ksl.Stanford.EDU>
Date: Wed, 13 Nov 2002 09:08:58 -0800 (PST)
Message-Id: <200211131708.gADH8wl29705@ksl.Stanford.EDU>
To: heflin@cse.lehigh.edu, hendler@cs.umd.edu, phayes@ai.uwf.edu
Cc: www-webont-wg@w3.org

Ontolingua has provided an ontology imports feature for a number of years.
In previous analysis that I did of knowledge bases for some large programs (such as DARPA's High Performance Knowledge Base program) with a LOT of KB developers distributed around the country, I observed a lot of cyclic inclusions.
That may be predictable because of the large, interconnected nature of the kb development.

What I also found when i was looking at KBs that were submitted to the libraries also supports jim's observation below.  Even simple uses of small new ontologies have naturally occurring cyclic inclusion of ontologies.

So this message has two points:
-  to reinforce the notion that cyclic imports will occur routinely.
- scaffolding systems allowing importing of ontologies have been available and in use for years.  (some/many? of those such as ontolingua have been updated to support daml+oil imports). 

We do not need more scaffolding built tin order to obtain usage data.

In a message dated 11/13/2002 9:57:53 AM Eastern Standard Time, hendler@cs.umd.edu writes:

Here's another one for you guys - really happened - I have two 
students who wanted their ontologies linked -  no changes involved 
  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.

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.
>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?)
>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.
>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?
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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)


Deborah McGuinness
Received on Wednesday, 13 November 2002 12:09:19 UTC

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