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Re: LANG: owl:ontology

From: Jim Hendler <hendler@cs.umd.edu>
Date: Sun, 15 Sep 2002 15:16:15 -0400
Message-Id: <p0511170bb9aa88fea022@[10.0.1.2]>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: www-webont-wg@w3.org

I was going to wait for others to weigh in before deciding to 
continue this, but I realized that there is some ambiguity and that 
perhaps Peter and I are making different assumptions:

>
>Peter wrote:  [snip
>In the current systems (DAML+OIL) ontologies are documents, at least as far
>as I can see.  Having ontologies be documents is a viable solution in my
>eyes, and provides an elegant solution to which information to import.
>[snip]
>
>The DAML+OIL documents are rather vague.  However, an imports refers to a
>URI and it seems to me that this means to import the contents of the
>document, as there is no other potential thing to import.

He is right that the document is vague - what it says is:


 From the DAML+OIL TR [1]
>Each daml:imports statement references another DAML+OIL ontology 
>containing definitions that apply to the current DAML+OIL resource. 
>Each reference consists of a URI specifying from where the ontology 
>is to be imported from. See the example above. Imports statements 
>are transitive, that is, if ontology A imports B, and B imports C, 
>then A imports both B and C. Importing an ontology into itself is 
>considered a null action, so if ontology A imports B and B imports 
>A, then they are considered to be equivalent.


I have been assuming that when I define a daml:ontology (which gets 
its own URI) then an import statement points at that definition, not 
at the document which it appears in.   Thus, when Peter says "this 
means to import the contents of the document" I don't think I agree. 
I think it means to import those statements that appear associated 
with the ontology URI (not the document URL) and that it may be an 
unwarranted assumption to assume that all the triples of any type 
appearing in the rdf:RDF of that document are necessarily assumed to 
be part of the ontology.

Jeff's use of the daml:imports as magic syntax [2] primarily focused 
on people wanting to import everything, but some of the mail on the 
original thread (see [3] and the many threads around it that it 
spawned and/or spawned it) pointed out the desire to only include 
some properties without importing the whole ontology (using cyc as an 
example). For an example of someone using stuff from other ontologies 
without importing see [4] and there's lots of other examples out in 
the real web (this is one of my students, so I got to see it, and 
then went seaching and found many more - in fact, I can find very few 
ontologies defined since the original Darpa set that use 
"daml:imports")

I'm looking for a solution that makes it clearer what is imported, 
and allows some control over that.
  -JH
p.s. I have answers to Peter's challenge of what gets included given 
my scheme, but I'll wait until I see whether other people care about 
this issue before sending yet another long note...



[1] http://www.w3.org/TR/daml+oil-reference#imports-def
[2] 
http://www.w3.org/2001/sw/WebOnt/webont-issues.html#I5.6-daml:imports-as-magic-syntax
[3] http://lists.w3.org/Archives/Public/www-rdf-logic/2002Apr/0060.html
[4] http://glue.umd.edu/~aloomis/498x/hw1-ont.n3
-- 
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 Sunday, 15 September 2002 15:16:40 GMT

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