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Fwd: Re: Comment on non-global keys

From: Jim Hendler <hendler@cs.umd.edu>
Date: Wed, 7 May 2003 11:52:20 -0400
Message-Id: <p05200f11badedc0e1f9a@[]>
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
>	autolearn=ham version=2.53
>X-Spam-Checker-Version: SpamAssassin 2.53 (
>[+cc sandro, who's now helping me with WG stuff...
>Sandro, we're working on our response to
>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
>shorthand notation for OWL Lite constraints
>From: Christopher Welty (welty@us.ibm.com)
>Date: Thu, Oct 10 2002
>>  >
>>  >>  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
>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] 
>>  >
>>  >>
>>  >>  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)
Received on Wednesday, 7 May 2003 11:52:34 GMT

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