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Re: SEM: Light review of semantics document

From: Jim Hendler <hendler@cs.umd.edu>
Date: Sat, 9 Nov 2002 18:59:14 -0500
Message-Id: <p05111707b9f34d260a8c@[10.0.0.45]>
To: Christopher Welty <welty@us.ibm.com>, www-webont-wg@w3.org

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
>data.
>
>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



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

<rdf:RDF>
   <chris:person rdf:id="Hendler" />
</rdf:RDF>

by the definition "uses owl terminology" this is NOT and owl 
document.  By the definition "uses terms from an owl ontology" this 
is an Owl document.

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.
   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.

  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.

  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.

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].

[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





>Dr. Christopher A. Welty, Knowledge Structures Group
>IBM Watson Research Center, 19 Skyline Dr.
>Hawthorne, NY  10532     USA
>Voice: +1 914.784.7055,  IBM T/L: 863.7055
>Fax: +1 914.784.6078, Email: welty@us.ibm.com
>
>
>
>
>pat hayes <phayes@ai.uwf.edu>
>Sent by: www-webont-wg-request@w3.org
>11/08/2002 11:34 AM
>
>         To:     Jim Hendler <hendler@cs.umd.edu>
>         cc:     www-webont-wg@w3.org
>         Subject:        Re: SEM: Light review of semantics document
>
>
>
>
>>Sorry Pat, but I gotta agree with Jeff on this one- you signed onto
>>this group which had "ontology" in the title, fully knowing by
>>charter we would create something called an ontology language.
>
>Well, sure, but apparently what you and Jeff meant by 'ontology'
>wasn't what I meant. Thats the trouble with English, right? Which is
>one reason why we are doing all this in the first place...
>
>><owl:ontology>
>>    statements
>></owl:ontology>
>>
>>was in DAML+OIL, has been in OWL from day 1, a prereq for WG members
>>was familiarity w/D+O, so you should have been aware that was there.
>
>I have no problem with that, but I have always understood this to
>simply be an XML marker for the presence of OWL syntax in the RDF
>graph. Why do we need to say anything more than that? "owl:ontology"
>isn't in the graph, right? So its not in the namespace, and it has no
>semantics. If "owl:ontology" is in the OWL namespace, then we ought
>to say what an RDF triple which includes that name means.
>
>>The issue we need to address is that IN ENGLISH USAGE (not formal logic)
>
>I do wish you would make at least an effort to disguise your built-in
>anti-logical knee-jerk, Jim. It just gets in the damn way. What we
>are all doing here, whether you like it or not, is using ENGLISH to
>talk ABOUT a FORMAL logical language. When using ENGLISH it is often
>a good idea to use words which refer to concepts that actually make
>some sense in the context being talked about.
>
>>there is a need for us to say whether there is a difference between
>>documents that look like
>>
>><rdf:RDF>
>>
>><owl:ontology ... />
>>...
>>
>><owl:class rdf:about="Moose">
>>    <owl:restriction>
>>      etc
>>    </owl:restriction>
>></owl:class>
>>
>></rdf:RDF>
>>
>>and documents that look like
>>
>><rdf:RDF>
>>
>><a:Moose rdf:id="MyMoose />
>>
>></rdf:RDF>
>>
>>(and those which mix some of both).
>
>The difference is that one of them contains OWL syntax and the other
>does not. End of story.
>
>What about the many other cases, such as  <rdf:RDF>....</rdf:RDF>
>which contains non-ground RDFS, say? What about one of those that
>contains RDFS which would break fast-OWL? What do we call those?  If
>some RDF uses rdf:bag, is it instance data? What about an rdf:List,
>described using bnodes? You (and Jeff) are confusing two different
>distinctions: ground versus non-ground, and RDF vs OWL. That is a
>dangerous confusion to incorporate into an official terminology.
>
>>Jeff's usage is consistent with the outside world's usage, and I
>>suggest if we don't use it we will confuse everyone in the world
>>except for logicians
>
>I'm tempted to respond that anyone who you would classify as a
>non-logician is already confused in any case. But I won't.
>
>>-- given that, I'd suggest we use it -- i.e.
>>
>>Ontology documents are those that define classes and properties.
>>Instance documents are defined by using RDF to produce instances (or
>>individuals) that are members of those classes with those properties.
>
>Sorry, I object to this, because it doesn't make sense. You are
>presuming something that is false: that RDF can only be used to
>describe ground facts. We ought to use a naming convention that warns
>the world not to get this confused, rather than casting the confusion
>in stone.
>
>I know that RDF is often used for instance data, but it can be used
>for other things. I frequently meet people in the DAML community who
>are surprised to hear that RDF allows bnodes; there is deployed
>software with serious bugs arising from the misunderstanding that RDF
>is used only for ground facts.  Also, this convention makes nonsense
>of the fundamental presumption that one can merge RDF graphs. If
>OWL/RDF really is RDF then this terminological usage becomes
>nonsensical even when applied to actual documents. It already doesn't
>make any semantic or operational sense.
>
>Pat
>
>>
>>OWL documents include each or documents which combine both.
>  >
>>I'm happy if someone wants a different term for "instance" documents.
>>
>>I think the above is consistent with our current documentation.  I'm
>>happy to see someone suggest rewording the above (Written quickly
>>and not formally) in a way that is more technically correct -- but
>>this is how most of the rest of the world will refer to what we
>>have, so we should make it easy for them....
>>   -JH
>>
>>
>>
>>
>>
>>
>>   1:42 PM -0600 11/7/02, pat hayes wrote:
>>>>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
>>>>>
>>>>>   --
>>>>>  ---------------------------------------------------------------------
>>>>>   IHMC                                    (850)434 8903   home
>>>>>   40 South Alcaniz St.                    (850)202 4416   office
>>>>>   Pensacola                               (850)202 4440   fax
>>>>>   FL 32501                                        (850)291 0667 cell
>>>>>   phayes@ai.uwf.edu                 http://www.coginst.uwf.edu/~phayes
>>>>>   s.pam@ai.uwf.edu   for spam
>>>
>>>
>>>--
>>>---------------------------------------------------------------------
>>>IHMC  (850)434 8903   home
>>>40 South Alcaniz St.                                           (850)202
>4416   office
>>>Pensacola                                                      (850)202
>4440   fax
>>>FL 32501  (850)291 0667    cell
>>>phayes@ai.uwf.edu                       
>http://www.coginst.uwf.edu/~phayes
>>>s.pam@ai.uwf.edu   for spam
>>
>>
>>--
>>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
>
>
>--
>---------------------------------------------------------------------
>IHMC  (850)434 8903   home
>40 South Alcaniz St.                                             (850)202
>4416   office
>Pensacola                                                        (850)202
>4440   fax
>FL 32501  (850)291 0667    cell
>phayes@ai.uwf.edu
>http://www.coginst.uwf.edu/~phayes
>s.pam@ai.uwf.edu   for spam


-- 
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 Saturday, 9 November 2002 18:59:28 GMT

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