- From: Jim Hendler <hendler@cs.umd.edu>
- Date: Wed, 7 May 2003 11:52:20 -0400
- To: webont <www-webont-wg@w3.org>
OOPS, a couple of messages didn't cc to webont -- bringing the discussion back to the list... >Subject: Re: Comment on non-global keys >From: Dan Connolly <connolly@w3.org> >To: Jim Hendler <hendler@cs.umd.edu> >Cc: Ian Horrocks <horrocks@cs.man.ac.uk>, Guus Schreiber <schreiber@cs.vu.nl>, > Sandro Hawke <sandro@w3.org> >Organization: World Wide Web Consortium (http://www.w3.org/) >Date: 07 May 2003 10:30:34 -0500 >X-Spam-Status: No, hits=-33.0 required=5.0 > tests=EMAIL_ATTRIBUTION,IN_REP_TO,QUOTED_EMAIL_TEXT, > QUOTE_TWICE_1,REFERENCES,REPLY_WITH_QUOTES, > USER_AGENT_XIMIAN > autolearn=ham version=2.53 >X-Spam-Level: >X-Spam-Checker-Version: SpamAssassin 2.53 (1.174.2.15-2003-03-30-exp) > >[+cc sandro, who's now helping me with WG stuff... >Sandro, we're working on our response to >http://lists.w3.org/Archives/Public/public-webont-comments/2003May/0019.html >] > >On Wed, 2003-05-07 at 09:58, Jim Hendler wrote: >> Ian - >> I am okay with the content of this reply -- but I'm a little >> concerned about the tone > >Umm... I'm not sure it's the tone that bothers me, but it >seems to just say "that's the way it is" without saying >why. If we're to decline his request for this feature, >we owe him a rationale that we think might reasonably >satisfy him. And I'd like to see more connect to >the WG proceedings. > >The first bit is quite good... > >[...] >> >Asserting that F is an InverseFunctionalProperty is just syntactic >> >sugar for an assertion that Thing is a subclass of restriction(inv-F >> >maxCardinality(1)), where the property inv-F is the inverse of >> >F. > >... but it would be much better if the connection between >InverseFunctionalProperty and maxCardinality were excerpted >from the spec. > >It's *almost* explained in reference: > http://www.w3.org/TR/owl-ref/#InverseFunctionalProperty-def >but not quite. > >So I suggest that our reply should say "here's the text >we're adding to reference to make this more explict..." > > >> Using such an assertion with classes other than Thing gives the >> >ability to "localise" the inverse functionality to particular classes, >> >and thus to provide a form of localised keys. E.g., >> >subClassOf(Employee restriction(inv-hasSSN maxCardinality(1))) would >> >make hasSSN a key for instances of Employee. >> > >> >Of course all these forms (including the use of >> >InverseFunctionalProperty) are in OWL Full if >> >InverseFunctionalProperty is a DatatypeProperty. >> > >> > >> >> The property we have in mind for specifying a key >> >> would have domain Class and range Property. One >> >> might call it something like 'hasKey' or 'classHasKey'. >> >> However, if we are broad-minded, we will recognize >> >> that sooner or later we will also want to support >> >> compound keys. So perhaps it could be called >> >> 'hasSimpleKey' or 'hasAtomicKey'. >> > >> >In an effort to avoid syntax "bloat" in OWL, the working group have >> >deliberately avoided trying to provide dedicated syntax for idioms >> >that can already be expressed using the language primitives. The >> >thinking is that tools will provide idioms appropriate to the >> >applications for which they are designed and generate the relevant OWL >> >syntax. > >When speaking for the WG, *always* use the WG's words; >i.e. cite the record and excerpt from it. > >The record of this "thinking" is >http://www.w3.org/2001/sw/WebOnt/webont-issues.html#I5.16-Feature-decision-for-CL1-cardinality > >-> > >shorthand notation for OWL Lite constraints >From: Christopher Welty (welty@us.ibm.com) >Date: Thu, Oct 10 2002 >http://lists.w3.org/Archives/Public/www-webont-wg/2002Oct/0063.html > >> > >> >> When n-ary relational tables are converted into RDF >> >> format, each table maps to a class and each of a table's >> >> columns maps to a property. If a table has >> >> a compound key (a rather common-place occurrence), >> >> then one would like to be able to map its key >> >> restriction to RDF as well. That would require >> >> that we support the notion of a compound key. For >> >> example, the class EmployeeHistory might have the >> >> key <hasSSN, historyDate>. >> >> >> >> A property representing a compound key declaration >> >> might map a Class to a List. Perhaps this property >> >> could be called 'hasCompoundKey'. >> > >> >Compound keys cannot be represented in OWL, and the ability to do so >> >would require a significant extension to the existing language. > >I assume you're right, but let's see if we can connect that >to the proceedings of the WG better. > >Comments of the form "your design doesn't let me do X" fit >best into the WG process as "please add X to your requirements". > >With a bit of a stretch, compound keys can be connected >to objective 015. Complex data types >http://www.w3.org/TR/webont-req/#obj-complex-data-types > >so I think this shows that the WG has considered this requirements >and not accepted it. > >Or is that too much of a stretch? > >I don't see much in the way of new information, so I think the >chairs should decide that this doesn't merit re-opening that decision. > >Moreover, in the status section, we see: > >"Requests for significant changes to the requirements are not >anticipated and will be evaluated in the context of the scope and >schedule of the Web Ontology Working Group charter and other plans for >the W3C Semantic Web Activity (Activity Statement)." > -- http://www.w3.org/TR/webont-req/ > > > >> > >> > >> >> >> >> Provisions for supporting key declarations appear >> >> in the OWL "wish list". Given how fundamental they >> >> are in real-world modelling, they ought to become >> >> more than that. >> > >> >As discussed above, keys can be defined in OWL full. Support for >> >compound keys is the subject of ongoing research (see [1]) and it is >> >not planned to include them in the current version of OWL. >> > >> >Regards, Ian >> > >> >[1] >>http://www.cs.man.ac.uk/~horrocks/Publications/download/2003/LAHS03a.pdf >> > >> >> >> >> Cheers, Bob >-- >Dan Connolly, W3C http://www.w3.org/People/Connolly/ >office: tel:+1-617-395-0241 (new VoIP phone Mar 2003) >mobile: tel:+1-816-616-6576 >mobile: mailto:connolly+pager@w3.org > -- 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 Wednesday, 7 May 2003 11:52:34 UTC