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RE: DAML+OIL: Questions & Improvements.

From: Dickinson, Ian J <Ian_J_Dickinson@hplb.hpl.hp.com>
Date: Fri, 26 Jan 2001 10:17:58 -0000
Message-ID: <5E13A1874524D411A876006008CD059F15C484@0-mail-1.hpl.hp.com>
To: "'King . Dany'" <DKing@drc.com>, "'www-rdf-logic@w3.org'" <www-rdf-logic@w3.org>
Hi Dany,
Regarding your question 5, it seems to me that you're confusing two things
(given my limited and still evolving understanding of ontologies and
DAML+OIL).  Class, property and instance are the modelling primitives
provided by RDF.  They provide a meta-language for defining an ontology,
part of which is a hierarchy of concepts.  The most general concept is (in
DAML+OIL) "Thing".  Every modelled concept is a Thing. The least general
concept is "Nothing". No modelled concept is a Nothing.  Concepts are
related by a number of different relations, one of which is sub-class.  If A
is a sub-class of B, every B is an A, but not vice-versa.  So the bug in the
example, imho, is that Animal should be a sub-class of Thing.

Relations like subClassOf, complementOf, etc, are intended to describe
relationships among concepts.  Given the modelling meta-language, concepts
are modelled as RDF classes.  Therefore the rdf:type relation is being used
to denote precisely that: every concept (Thing, Animal, etc) is modelled as
rdfs:Class.  But because it's part of the metalanguage, rdfs:Class does not,
in fact, appear in the concept hierarchy.

As far as I can tell from the various versions, at one time DAML relations
like type were considered distinct from RDFS and RDF relations. Then in the
2000/12 version, where there were overlaps in terminology, the RDF or RDFS
relations were used in preference. It seems to me that you're pointing out a
potential problem with this, which is:
   Thing rdf:type rdfs:Class
means "concept Thing is modelled as an RDFS Class", whereas
   adam rdf:type Person
means "instance adam belongs to the concept Person".

Perhaps the "logical elders" (:-) on this list would like to comment?

By the way, I like your proposal on the version info element.


> -----Original Message-----
> From: King . Dany [mailto:DKing@drc.com]
> Sent: 25 January 2001 20:37
> To: 'www-rdf-logic@w3.org'
> Cc: TeamXML; Randolph . Wayne
> Subject: DAML+OIL: Questions & Improvements.
> The following questions/comments are about the DAML+OIL 
> ontology version 1.6
> 2001/01/11.
> [... elided for brevity ...]

> 5) The "Thing" class is not implemented properly.   The 
> "Thing" class is
> supposed to be the base class in DAML+OIL, however, it is 
> currently just
> another class which has no direct connection to any other 
> class.  Per the
> current DAML+OIL specification, the "rdf:Class" is the base class in
> DAML+OIL.  Please review the attached PowerPoint presentation 
> regarding the
> problem (each slide has important notes).  Also, there are 
> two solutions
> described therein.  The Alternative Solution B is the most 
> concise and is
> preferred.
>  <<Thing.ppt>> 

> ...

Ian Dickinson    HP Labs, Bristol, UK    mailto:Ian_Dickinson@hp.com
Received on Friday, 26 January 2001 05:18:11 UTC

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