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Re: new version of semantic layering document

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Mon, 23 Sep 2002 06:54:08 -0400 (EDT)
Message-Id: <20020923.065408.68538365.pfps@research.bell-labs.com>
To: phayes@ai.uwf.edu
Cc: www-webont-wg@w3.org

On a quick read through of part of the new document I found the following
issues.  I'm assuming that rdfs:subClassOf, rdfs:subPropertyOf,
rdfs:domain, and rdfs:range are strengthened to iff.  Without this
strengthening, many more of the claims in the document are incorrect.

- owl:UniqueProperty is not in OWL.

- Making IOC and IOP sets of sets doesn't seem to have any impact.  The
  fact that ICEXT(IS(owl:Class)) is a set of sets doesn't make ICEXT(IS(foo))
  have any relationship to IS(foo), for foo in ICEXT(IS(owl:Class)).

- owl:DisjointWith is incorrect.  There is no reason to require that the
  disjoint classes be nonempty.

- Care has to be taken with lists that contain elements of LV.

- Weak OWL only requires the existence of unions, intersections, finite
  sets, and complements.  This means that (someValuesFrom foo bar) does not
  necessarily exist.

- It is not the case that Weak OWL requires IOC to contain all finite
  subsets and be closed under union, intersections, and relative
  complements.  All that is required is that for each such set, IOC
  contains an element whose class extension is that set.

- In a Weak OWL interpretation it is not the case that 
      owl:Thing rdf:type owl:Class .
      owl:Nothing rdf:type owl:Class .
  In general Weak OWL does not force any particular class to belong to
  owl:Class.  The claim that owl:Thing, owl:Property, and owl:Class are
  analogues to rdfs:Resource, rdfs:Class, and rdf:Property is incorrect.
  Further, all of
	owl:Class rdfs:subClassOf rdfs:Class .
	owl:Restriction rdfs:subClassOf owl:Class .
	owl:Property rdfs:subClassOf rdf:Property .
 are not true in Weak OWL, nor is 
	AAA rdf:type owl:Property .  ->  AAA rdfs:domain owl:Thing .
 a valid inference in Weak OWL.

- In Large OWL it is not the case that owl:Class and rdfs:Class have the
  same extension.  In particular owl:Nothing (and indeed most empty
  classes) can belong to neither, either one or, or both of owl:Class and
  rdfs:Class in Large OWL.  It is thus not the case that IOC=IC or IOP=IP
  in Large OWL.

- The closure conditions for Large OWL should change integer to
  non-negative integer.

- There are many restrictions in Large OWL that may be problematic because
  their presence may affect their extension.  For example, what is the
  class extension of  
      _:x owl:onProperty rdfs:subClassOf .
      _:x owl:maxCardinality 57 .
  Can it be shown that there are *no* problems in determining the class
  extensions of all the restrictions that mention the RDF and RDFS
  structural properties and that thus may interfere with their own class
  extension?

These are all the issues that I could find in a quick partial reading of
the document.

peter

PS:  I would much have preferred to try to get a version of the previous
     document that didn't have any known bugs before making such drastic
     changes. 
Received on Monday, 23 September 2002 06:54:17 GMT

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