- From: Deborah McGuinness <dlm@ksl.stanford.edu>
- Date: Mon, 11 Nov 2002 10:37:33 -0700
- To: Christopher Welty <welty@us.ibm.com>
- CC: www-webont-wg@w3.org
I have had a lot of discussions with people about what ontologies are in common usage. I think the only thing that we all agree on is that there is a spectrum of descriptions for ontologies. I dont know that we want to get into a big description of it since i dont think the discussion is short. if people want to refer to something on the topic, i wrote about it in an "ontologies come of age" paper [1]. that paper includes a spectrum that a number of us came up with and i refined after a panel at aaai on ontologies. Thus, i would be careful below with wording such as ontologies referring "to what we "traditionally" ... call ontology in Computer Science, and "knowledge base" to refer to a mixture of ontology and instance data." including class descriptions in our ontologies means including some instances because of hasValue and oneOf. Since someone will ask the question - I wanted to head it off here. We should NOT say that owl documents with instances in them are not to be referred to as ontologies. I agree with jim's point though that a document with only instances and their associated class tags in it is not what i think of as an ontology and also is not something that i would like to promote as a way of using the term. i am not opposed to instance data set for this. i do not usually make a big deal of a distinction between knowledge bases and ontologies since the overlap is too great and many people consider knowledge bases ontologies. I had not thought about this point directly in the guide writing but it probably would not create as much confusion if we downplay that distinction in the guide. deborah [1] http://www.ksl.stanford.edu/people/dlm/papers/ontologies-come-of-age-abstract.html Christopher Welty wrote: > Jim, > > If by, "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," you mean that you just want a term that we will > agree to employ in our human interchange, and not something in the OWL > language, then that's fine, make something up and we'll add it to the > Guide. > > It appeared from the discussion that Jeff and you wanted something more > formal, that required an adjustment to the meaning of the owl:ontology > tag. > > In the Guide, Mike and I chose to employ "ontology" (not the tag, but the > natural language term) to refer to what we "traditionally" (it's a short > tradition) call ontology in Computer Science, and "knowledge base" > to refer to a mixture of ontology and instance data. We did not draw > the distinction you want there, but if I understand you > correctly, the Guide is right place to talk about this. > > -Chris > > 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 > > Jim Hendler <hendler@cs.umd.edu> > Sent by: www-webont-wg-request@w3.org > 11/09/2002 06:59 PM > > To: Christopher Welty/Watson/IBM@IBMUS, www-webont-wg@w3.org > cc: > Subject: Re: SEM: Light review of semantics document > > > > 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 -- Deborah L. McGuinness Knowledge Systems Laboratory Gates Computer Science Building, 2A Room 241 Stanford University, Stanford, CA 94305-9020 email: dlm@ksl.stanford.edu URL: http://ksl.stanford.edu/people/dlm (voice) 650 723 9770 (stanford fax) 650 725 5850 (computer fax) 801 705 0941
Received on Monday, 11 November 2002 12:34:03 UTC