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   Re: [xml-dev] Beyond Ontologies

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Simon St.Laurent wrote:

>tpassin@comcast.net (Thomas B. Passin) writes:
>>Anyone have an
>>example where a new distinction, giving rise to a new
>>__classification__ term, spread rapidly?
>What exactly qualifies as a classification term?
Anything which defines a set of things i.e. a class. For example: things 
which are of  rdfs:type owl:Class . The term which identifies any of 
these classes is it's URIref .

>I'd expect fashion ontologies, for instance, to change constantly, at
>least the ones which classify style.
I'd like to clarify a few points:

1) There is nothing that prevents ontologies from changing fairly 
regularly. Ontologies themselves are just :-) documents, representations 
of resources :-) that can change as often as the author desires. 
Ontologies can be generated from databases etc. The only tricky point of 
this is designing systems that can deal with changing ontologies, but 
that is a software issue, not necessarily an ontology issue. In any case 
the WebOnt WG, which has a good number of people who have lots of 
experience with ontologies has considered these issues, indeed from the 
"use cases and requirements" document: 
http://www.w3.org/TR/webont-req/#goal-evolution . Note *requirements* R3 
"explicit ontology extension" and R6 "versioning information" which are 
relevent to this issue.

2) although the world is constantly changing, relationships need not so 
constantly change. For example, *you* and *your father* -- I don't need 
to know any details about you, nor about your father, and indeed both 
you and your father are constantly changing -- even for deceased people, 
for example, the "time since birth" is a property whose value is in a 
constant state of change. "physical location" is another property which 
might be in a constant state of change etc. etc. Nonetheless, the 
*relationship* <#Simon> :sonOf _:1 between the two of you need not 
change (I haven't even assigned a URI to your father!)

The point about this is that the constraints imposed by any ontology do 
not (typically) result in any single state of affairs, rather a *range 
of states of affairs*. A good ontology might capture a wide range of 
states while at the same time imposing the proper constraints on these 

Admittedly time dependent changes in the state of the world remains an 
area of current research for ontologies, OWL/RDF in specific, but while 
OWL may not have detailed specific mechanisms for dealing with time 
dependent state changes, the fact that such state changes might be 
important has been factored into and considered in the design of OWL 
itself i.e. future extensions to OWL might indeed directly capture time 
dependencies. There is no reason that one should conclude that one has 
to throw out OWL, or move beyond OWL in order to model a changing world. 
Language itself is in a constant state of flux, yet Wordnet.



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