- From: Jim Hendler <hendler@cs.umd.edu>
- Date: Fri, 24 Jan 2003 17:26:28 -0500
- To: Ian Horrocks <horrocks@cs.man.ac.uk>, "Jeremy Carroll" <jjc@hplb.hpl.hp.com>
- Cc: "webont" <www-webont-wg@w3.org>
At 21:50 +0000 1/24/03, Ian Horrocks wrote: >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 Ian, that's reassuring (and thanks also to Peter C. for his earlier mail on the topic) -- I think that the WG needs to reach a decision, and particularly to make sure this gets into some document - JH > > >[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 >> > >> > >> -- 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 17:26:42 UTC