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Re: question: datatype reasoning?

From: Jim Hendler <hendler@cs.umd.edu>
Date: Wed, 29 Jan 2003 17:11:36 -0500
Message-Id: <p05200f2bba5dff4c4969@[]>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: www-webont-wg@w3.org

At 16:38 -0500 1/29/03, Peter F. Patel-Schneider wrote:
>From: Jim Hendler <hendler@cs.umd.edu>
>Subject: question: datatype reasoning?
>Date: Thu, 23 Jan 2003 21:25:50 -0500
>>  I was asked the following by a colleague, we tried to find the answer
>>  in the Semantics document, but we couldn't quite work out the
>>  details.  Question is, does a complete Owl Lite or DL reasoner have
>>  to do complete datatype reasoning?  i.e. for all the XML schema
>>  primitive types, does a complete OWL reasoner have to be able to do
>>  the correct class reasoning, etc -- knowing integers are numbers,
>>  URIs are strings, etc. and appropriately applying these.
>A complete OWL reasoner does have to do reasoning with numbers, etc.
>As Ian has pointed out, the design of OWL DL has been carefully worked out
>so that this is not as hard as one might think.
>>    If the answer is that an OWL system must do so, do we have any
>>  implementation evidence to offer in this space?  If we don't expect
>>  complete datatype reasoning, what level of such do we expect, and
>>  where will we specify it (document-wise)
>RACER handles lots of inferences with respect to such datatypes, in a
>even-more-powerful datatype theory.
>>    thanks
>>    JH

Speaking as chair:

Let me be even, even, even clearer -
  Which document says what is and is not expected to be implemented?
  Which document says what datatype inferences are required to be a 
complete reasoner for Lite, DL, Full?

The fact that DL and Racer can handle some datatypes is not what I am 
asking - I am asking exactly what an OWL reasoner is expected to do 
to be considered complete (or, rhetorically questioningly, are we 
giving up completeness as a requirement for Lite and DL, in which 
case why do they exist??)

In short, if this is in a current document - where is it?  If not, 
where will it go.  We cannot have a language specification that 
doesn't bother mentioning some large part of our spec.

If there is a particular datatype theory we expect, then we must 
specify it.  If these isn't, we must say what is expected

I don't see how we can go to LC with a major part of our expectations 
on implementations unspecified.

Taking off my chair hat -- personal opinion:
  I think that we shoudl try to set minimal expectations on datatype 
reasoning, letting good systems get a benefit by offering more, but 
still considering systems to be complete OWL reasoners if they don't 
handle all datatype cases -- I think we should basically say correct 
handling of strings and integers (w/some definition) is all that is 
required and leave everything else gravy.
  Otherwise, I think we can spend months arguing details

Consider this for your headache pleasure -- if I give you an 
allDifferent list with 366 instances of type xsd:date all of which 
have the same year, then this document is consistent if that year is 
a leap year, but inconsistent if it isn't (and I believe that 
specifying the axiomization of what is and isn't a leap year requires 
expressivity way beyond what we expect in an OWL reasoner.)

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, 29 January 2003 17:11:43 GMT

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