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

Re: SEM: Light review of semantics document

From: pat hayes <phayes@ai.uwf.edu>
Date: Tue, 19 Nov 2002 19:36:01 -0500
Message-Id: <p05111b08ba0086d758f7@[]>
To: Jim Hendler <hendler@cs.umd.edu>
Cc: www-webont-wg@w3.org

Sorry about delay in replying.

>At 3:00 PM -0500 11/8/02, Christopher Welty wrote:
>>I have to agree with Pat here, guys.  The meaning of an "owl:ontology" tag
>>inside an RDF document is simply that the document contains OWL syntax,
>>not some hard to pin down notion of a separation between definitions and
>>What you, Jeff and Jim, want to accomplish can be done with comments,
>>since the distinction you want does not exist in the language nor in its
>>interpretation - it only exists in the minds of some people.  I think what
>>you want is sort of like the distinction C compilers make for ".h" files -
>>in point of fact there is no difference between  the contents of a ".h"
>>and ".c" file, just a methodology enforced by some compilers.
>>That using "ontology" to describe a set of instances does not match your
>>definition is not, I think, the point.  Maybe the tag is inappropriately
>>named.  But don't get me started on mis-named tags.  "Property" is already
>>a LOT worse.
>Chris/Pat - I think you guys misunderstood me - I believe that all 
>of these things are OWL documents, but I'm concerned with a small 
>matter of usage.  The way I see it, there are documents which are 
>clearly owl ontologies because they define terms and properties and 
>the like. There are also owl documents that only use those terms

There are also RDF and RDFS documents that use those terms. So? I 
thought y'all *wanted* things to work out that way, that is supposed 
to be part of the layercake, right? So that people can use these 
languages together all nice and smoothly. That's why we went to all 
this trouble in the model theory.... Do you have a problem with this, 

>and, in fact, there is no reason that there will be any trace of any 
>OWL vocabulary in those documents.

Well then they won't be OWL documents. They will be be, say, RDF 
documents that use a vocabulary defined (yech, I hate that word) in 
another document that uses OWL.

>  For example, if Chris defines an ontology about people, I could 
>have a document which contains only the following:
>Namespace definitions to RDF and to Chris' document
>   <chris:person rdf:id="Hendler" />
>by the definition "uses owl terminology" this is NOT and owl document.

Right, its not.

>  By the definition "uses terms from an owl ontology" this is an Owl document.

Well, but that strikes me as a silly and unworkable idea. Is this 
transitive? Suppose some RDF doc uses a term from another RDF doc 
that uses a(nother) term from a(nother) RDF doc which uses.... and 
200 steps along this, we meet some OWL. Does that make the first one 
an OWL document? What if we also meet some DAML and some RDFS and 
some OWL and something else altogether?

>So I am asking for terminology that would
>    i. let me differentiate this document from an arbitrary RDF 
>document (and Pat, please note I wasn't being anti-logical, but it 
>seems to me we don't need this distinction to have a logical meaning 
>in the formal sense -- I'm simply looking for a common term to mean 
>RDF documents that are expecting to be linked to owl ontologies) -- 
>Jeff called this a data document, which Pat didn't like.

I don't see any need to say anything other than that it is an RDF 
document. The vocabulary it uses might also occur in some OWL or some 
DAML or some RDFS or even in some FOODLE which hasn't been invented 
yet. As long as they all extend RDF, things should work smoothly.

>   ii. lets me differentiate this kind of document from an owl 
>document which does contain class and property definitions and 
>restrictions.  I DO KNOW what to call the ones that have that (an 
>ontology), but not what to call the other ones.

Er... RDF? Like I said, wasn't that the whole point??

>  I believe strongly that this is not a critical issue of language 
>design, it's simply a suggestion we develop consistent terms so we 
>get our message out.
>Technically, it is clear to me the document above is an RDF document 
>- it would use the RDF Model Theory and all would be happy.  But 
>colloquially, we need to be able to discuss these documents with a 
>term that people in the outside world can understand.

Why can't they understand our calling them RDF? The RDF people 
already want to say that RDF includes any forms of meaning defined in 
any way whatever.

>  In class, I refer to these as "Owl data sets" and the students get 
>it, I'd be happy with that term.
>So, I ask Pat/Chris and anyone else inclined to help out:
>  what name shall we use for documents that are in the class with the 
>following properties:
>Document a rdf:RDF document AND
>Document uses terms from a owl ontology document AND
>Document NOT a owl ontology document.
>IMHO, If we call such a document an "ontology," we're going to 
>confuse  a lot of people.

Call it an RDF document, and hold your head high and stick out your 
chin as you do so.

>Finally, such documents not only will, but DO exist (in case someone 
>is going to argue that this is specious) -- there's a number of 
>examples in [1], for example [2] which has no hint of the daml 
>namespace in it, but is linked to an ontology which is clearly 
>defined in DAML [3].

Great, it all seems to be working.


>[1] http://www.daml.org/data
>[2] http://www.daml.org/2002/02/chiefs/af.daml
>[3] http://www.daml.org/2002/02/chiefs/chiefs-ont

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Received on Tuesday, 19 November 2002 19:36:03 UTC

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