- From: Ivan Herman <ivan@w3.org>
- Date: Tue, 27 Nov 2007 13:00:08 +0100
- To: Jim Hendler <hendler@cs.rpi.edu>
- Cc: Boris Motik <boris.motik@comlab.ox.ac.uk>, 'OWL Working Group WG' <public-owl-wg@w3.org>
- Message-ID: <474C06C8.6020601@w3.org>
Jim Hendler wrote: > Le me be clear, I didn't agree I liked this solution, I agreed it was > the minimal solution under current constraints :-) > What I do agree with Boris on is that I see no reason to allow punning > of object and datatype properties - these are inherently different than Well... I did meet one example. DCMI (the organization behind the Dublin Core metadata) is having problems exactly on that. They have an abstract model document[1] where they speak about 'value surrogate' that can either be a literal or non-literal. When mapping this abstract model to RDF[2] they hit this problem (eg, is the value of a dcterm:subject property a literal or not). _At the moment_ their terms are not yet defined in OWL, but they were thinking about it. The strict separation of datatype and object properties was a problem they already realized they have (they are not really happy having two different property names for 'subject' for example). Punning may be an answer to their concerns. Ivan [1] http://dublincore.org/documents/abstract-model/ [2] http://dublincore.org/documents/dc-rdf/ > the class/instance punning, which is based on a known KR feature > (metamodeling - which got its own WG Note from the dissemination SWBPD > WG). Again, I've yet to see any use case where this kind of punning is > useful - I have seen some in some advanced KR systems where morphing > from one to the other is doable, but I don't see us taking OWL anywhere > near that far into pi-logic space. > > On Nov 21, 2007, at 4:31 AM, Boris Motik wrote: > >> >> Hello, >> >> I do agree that duplication of vocabulary is rather nasty. I've spoken >> to Jim Hendler at ISWC about it, and we came to a possible >> solution, which I'd like to overview next. Before giving the solution, >> however, let me just recapitulate why we introduced the >> duplicated vocabulary in the first place. >> >> 1. OWL 1.1 allows the same URI to be used as both an object and as a >> data property. (OWL 1.1 in general allows for punning; however, >> for this particular problem, only punning on object and data >> properties is a problem. Thus, let us not discuss here the general >> problems of punning in OWL 1.1 - this should be discussed separately.) >> >> 2. Parsing OWL RDF is difficult: one needs to first scan the file for >> the appropriate rdf:type triples, after which one needs a >> second pass to actually output the axioms. Assuming that you parse >> just one ontology, this is a pain but not a serious problem; >> however, ontology imports exacerbate this problem. Assume that you are >> parsing an ontology O that imports an ontology O'. >> Furthermore, let us assume that O contains, for example, a >> someValuesFrom restriction on the property p. In OWL 1.0 it can happen >> that the triples in O do not allow us to disambiguate the type of p; >> thus, we need to look at the imported ontology O' to find out >> what the correct type of p is. This makes parsing of OWL RDF really >> difficult: you can't process an ontology by itself, but you need >> to look at the imported ontologies as well. >> >> Even worse, what if the imported ontology O' is not in OWL RDF but in >> some other format? (For example, KAON2 allows a file ontology >> to import an ontology that resides in a relational database.) Parsing >> is now next to impossible. Thus, to allow parsing an ontology >> O by looking only at the triples in O, we introduced the typed vocabulary. >> >> >> --------------------------------------------------------------- >> >> And now for the solution. >> >> I do agree that the first point is not really a use-case: I do not >> expect that users will actually want to use the same URI as both >> an object and a data property. In contrast, being able to parse each >> ontology by itself seems like a desirable property that should >> be preserved. Hence, I propose to change the specs as follows: >> >> 1. I would leave the structural specification as it is. In this spec, >> I would allow the same URI to be used as both an object and a >> data property, and I would leave the typed vocabulary as it is. This >> is not so much driven by the desire for punning; rather, the >> structural specification is intended to provide guidance for >> implementors of OWL APIs. In all APIs I know of, you do have a >> separation of object and data properties; therefore, we should keep >> this separation in the spec as well. Whether you then allow the >> same URI to be used as an object and as a data property is then really >> irrelevant for all intents and purposes. >> >> 2. A transformation of an ontology from the structural format (i.e., >> from the functional-style syntax) into RDF should be possible >> only if you strictly separate the properties into object and data ones. >> >> 3. The transformation into RDF would then be roughly the same as in >> OWL 1.0, with the following difference: the resulting RDF graph >> would be *required* to type all properties used in the graph. >> >> 4. An RDF graph G could be parsed into the structural format only if >> each URI that is used as a property is correctly typed IN THIS >> GRAPH. If, for example, some URI p is used in a someValuesFrom >> restriction but G contains neither <p rdf:type owl:ObjectProperty> >> nor <p rdf:type owl:DatatypeProperty>, then G would not constitute a >> valid OWL 1.1 DL ontology. >> >> >> This solution seems to have the benefit of satisfying everyone: we can >> parse each RDF graph by itself, there is no typed vocabulary, >> and most reasonable use cases seem to be satisfied. Let me know how >> you feel about this solution. >> >> Regards, >> >> Boris >> >> >>> -----Original Message----- >>> From: public-owl-wg-request@w3.org >>> [mailto:public-owl-wg-request@w3.org] On Behalf Of OWL Working >>> Group Issue Tracker >>> Sent: 20 November 2007 14:49 >>> To: public-owl-wg@w3.org <mailto:public-owl-wg@w3.org> >>> Subject: ISSUE-65 (excess vocab): REPORTED: excessive duplication of >>> vocabulary >>> >>> >>> >>> ISSUE-65 (excess vocab): REPORTED: excessive duplication of vocabulary >>> >>> http://www.w3.org/2007/OWL/tracker/issues/ >>> >>> Raised by: Jeremy Carroll >>> On product: >>> >>> >>> The member submission documents seem to replace a good many >>> properties from OWL 1.0 with three >>> properties in OWL 1.1. (The old version, and two new versions, one >>> for data properties, and one for >>> object properties) >>> >>> This: >>> - creates additional work for implementors >>> - creates additional work for documentation writers >>> - potentially creates confusion for people as they learn the language >>> >>> Do the benefits outweight these (and other) costs? >>> >>> >>> >>> >>> >> >> >> > > "If we knew what we were doing, it wouldn't be called research, would > it?." - Albert Einstein > > Prof James Hendler http://www.cs.rpi.edu/~hendler > Tetherless World Constellation Chair > Computer Science Dept > Rensselaer Polytechnic Institute, Troy NY 12180 > > > > -- Ivan Herman, W3C Semantic Web Activity Lead Home: http://www.w3.org/People/Ivan/ PGP Key: http://www.ivan-herman.net/pgpkey.html FOAF: http://www.ivan-herman.net/foaf.rdf
Received on Tuesday, 27 November 2007 12:00:18 UTC