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Re: SEM: Light review of semantics document

From: pat hayes <phayes@ai.uwf.edu>
Date: Thu, 7 Nov 2002 13:42:36 -0600
Message-Id: <p05111b17b9f06eeeb2ba@[65.217.30.130]>
To: Jeff Heflin <heflin@cse.lehigh.edu>
Cc: www-webont-wg@w3.org

>Pat, there is a terminology problem here. What you and Peter call
>ontologies are different from what I call ontologies.

Yeh, I had that impression. My problem is that I don't really know 
what you are talking about.  I have never come across any useful 
definition of "ontology" in our non-philosophical sense other than 
something like "set of sentences" or maybe a document containing a a 
set of sentences, etc.. If there is a real difference in your mind 
between ontologies and other OWL thingies, then we ought to get this 
clear and incorporate it into the language in some way.

>My practical
>definition is that OWL ontologies are only those OWL documents that
>include the <owl:Ontology> tag.

Hmm, I have to confess that I wasn't aware that 'owl:Ontology' was in 
the OWL namespace. What is it supposed to mean?? Does it appear in 
the RDF graph anywhere?

But OK, an ontology is a *document*. In what language? I'm guessing 
it has to be in  OWL/RDF/XML, right? So an OWL/RDF graph is not an 
ontology(?)

>All other OWL documents are not OWL
>ontologies. Now, you are correct that a document with <owl:Ontology>
>could consist of nothing but ground facts, and as such you don't
>technically need to have a separate class of document for data. However,
>the fact is, people only use the <Ontology> tag when they are defining
>vocabularies (this statement is based on common usage in DAML). Are you
>suggesting that these people should include <Ontology> tags is all of
>their documents (see daml.org's list of data sets for a number of
>examples of DAML documents without these tags)?

I really don't give a rats about this tag, to tell you the truth, but 
certainly people should somehow mark their OWL as being OWL; if they 
don't, then they can't complain if an OWL engine misses it entirely. 
We might want to follow RDF's lead and register an OWL media type, 
though I think that idea is wrong-headed, myself. All I care about is 
that we have some way to detect well-formed OWL which is being 
asserted. Well-formed OWL means what it means as defined by the OWL 
specs. The distinction between ground and non-ground OWL is 
unimportant, seems to me, and there is no need to even refer to it. 
If some piece of OWL has 10|6 ground facts and one non-ground fact, 
I'm cool with that. What would you call it? Data with a dash of 
ontology?

>Or are you suggesting
>that we should call these ontologies too?

If we use the term at all, then yes, they are ontologies, in much the 
same sense that a gazetteer is a book.

>  I think the later would really
>confuse users to call every document an ontology, but only some
>ontologies are <Ontology> ontologies. In any case, all of our documents
>need to be a lot more clear about terminology (e.g., which definition of
>ontology does our WG use) and about how people should use ontologies to
>describe real content.

As to the last point, the distinction between ontology and data just 
seems to make things more confusing, suggesting a distinction in 
meaning that isn't there.

Pat

>
>Jeff
>
>pat hayes wrote:
>>
>>  >pat hayes wrote:
>>  >>
>>  >>  >Here's some initial comments on the Semantics document dated Nov. 3:
>>  >>  >
>>  >>  >1) Sect. 2.2. The syntax needs the ability to represent documents that
>>  >>  >consist soley of facts (that is, something other than ontologies).
>>  >>
>>  >>  ? Can you explain what you mean by "other than ontologies" ?Do you
>>  >>  mean, not in OWL?
>>  >>
>>  >
>>  >Part of this depends on what you consider OWL. From your response, I
>>  >assume that you think of OWL as just a language for defining ontologies,
>>  >and that you must use it with RDF in order to describe data
>>
>>  No. I fail to see the distinction you are drawing between 'ontology'
>>  and 'data'. I don't know what you mean by this, or what importance it
>>  has. One can have valid OWL documents which consist of nothing but
>>  ground RDF facts. So?
>>
>>  >(e.g., a
>>  >product catalog, a univeristy's course offerings, etc.). I tend to think
>  > >of OWL as an extension to RDF, so this data is still part of OWL, it
>>  >just has the standard RDF syntax.
>>  >
>>  >In any case, our model theory must talk about data to the same extent
>>  >that it talks about ontologies.
>>
>>  It does. It always has done. What is the problem?
>>
>>  Pat
>>
>>  --
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Received on Thursday, 7 November 2002 14:42:26 GMT

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