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RE: question: datatype reasoning?

From: Ian Horrocks <horrocks@cs.man.ac.uk>
Date: Fri, 24 Jan 2003 21:50:43 +0000
Message-ID: <15921.46387.258372.404665@excalibur.horrocks.net>
To: "Jeremy Carroll" <jjc@hplb.hpl.hp.com>
Cc: "Jim Hendler" <hendler@cs.umd.edu>, "webont" <www-webont-wg@w3.org>

As Jeremy points out, reasoning with datatypes can be
hard/problematical. Fortunately, OWL Lite and DL have a cunning design
such that reasoning with datatypes is separated from "abstract"
reasoning. This means that:

1. an OWL Lite/DL reasoner is complete iff both the abstract part and
datatype part are independently sound and complete.

2. we can easily formalise what constitutes an "admissible" datatype,
i.e., one for which it is theoretically possible to provide a sound
and complete reasoner (see [1]).

3. a limited (in terms of datatypes supported) and/or incomplete
datatype reasoner would introduce a limited and easily characterised
form of overall incompleteness.

I think that we can expect many implementations to support only a
subset of the available datatypes, but given the above design it will
be easy to inform users as to just what such reasoners can do and
where they will be incomplete.

Ian


[1] http://www.cs.man.ac.uk/~panz/Zhilin/download/Paper/Pan-Horrocks-datatype-2002.pdf

On January 24, Jeremy Carroll writes:
> 
> 
> My understanding is as follows:
> 
> There are many difficult cases
> e.g.
> 
> <p> range xsd:negativeInteger
> <p> range xsd:byte
> 
> DL-entails
> 
> owl:Thing owl:sameClassAs
>   restriction(p, maxCardinality=128 )
> 
> There are worse cases when we are considering potential compatible types
> that do not have the same primitive base type (e.g. try xsd:float instead of
> xsd:byte). Such cases are in need of clarification from XML Schema WG.
> Nasty questions that can be asked in OWL DL assuming floats and decimals
> share the same underlying real values is how many floats are unsignedLongs
> (algorithm is keep increasing the maxCardinality in an entailment like that
> above until the entailment does not hold).
> 
> 
> I am not sure that there can be an effective OWL DL reasoner that cannot
> reason about the cardinalities of sets of individuals, and hence it may also
> need the ability to reason about the cardinalities of sets of datatypes (as
> in the above example).
> OWL Lite is largely rescued from this by restriciting cardinalities to 0 and
> 1. A complete OWL Lite reasoner would I suspect need to simply know the
> intersection lattice of the XML Schema builtin datatypes and which
> intersections are empty and singleton.
> 
> e.g.
> 
> <p> range xsd:nonNegativeInteger
> <p> range xsd:nonPositiveInteger
> 
> Lite-entails
> 
> owl:Thing rdfs:subClassOf
>   restriction(p, maxCardinality=1 )
> 
> or
> 
> <p> range xsd:unsignedByte
> <p> range xsd:nonPositiveInteger
> <i> rdf:type restriction( p, minCardinality=1 )
> 
> Lite-entails
> 
> <i> <p> "0"^xsd:int
> 
> OWL with user defined datatypes (that we want) is worse.
> OWL Full (with or without user defined datatypes) is much worse.
> 
> I was planning on adding such tests under the datatypes issue.
> 
> see:
> http://lists.w3.org/Archives/Public/www-archive/2002Nov/att-0092/02-index
> for long discussion of these issues (RDF not OWL)
> 
> 
> Jeremy
> 
> 
> > -----Original Message-----
> > From: www-webont-wg-request@w3.org
> > [mailto:www-webont-wg-request@w3.org]On Behalf Of Jim Hendler
> > Sent: 24 January 2003 03:26
> > To: webont
> > Subject: question: datatype reasoning?
> >
> >
> >
> > 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.
> >   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)
> >   thanks
> >   JH
> >
> >
> >
> >
> > --
> > 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 Friday, 24 January 2003 16:50:09 GMT

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