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WOWG: contentive comment summary

From: Jim Hendler <hendler@cs.umd.edu>
Date: Thu, 15 May 2003 19:09:05 -0400
Message-Id: <p05200f3ebae9c666015c@[]>
To: webont <www-webont-wg@w3.org>

Guus and I have been sorting through the comments looking for those 
where the WG may have to be in the critical path.  We've identified 
the ones below as most likely to either raise or reopen an issue.  We 
will be sending individual messages asking various editors or other 
WG members to "volunteer" to write responses (to submit back to the 
WG - not to the public-list without an okay first) - the below is to 
let everyone know what the list is and to solicit comments on those 
you feel strongly about.  There are many other comments not on this 
list, and we hope the editors will keep working on those in the way 
you've been doing so far -- we've made a dent, but there's a long way 
to go (*sigh*) - some of these have already been assigned -- in that 
case they say ASSIGNED: and to whom...

General LC comments
overview 13 May

RDFCore: Comments on OWL Reference - owl:class not needed

     It has been suggested to
     RDFCore that owl:Class is not needed.  RDFCore requests the
     creation of test cases to clearly illustrate the differences
     between owl:Class and rdfs:Class.
RDFCore: Comments on OWL Reference - more readable RDF mapping

     RDFCore requests that the specifications be amended to include a
     description of necessary conditions for a RDF document to be in
     OWL DL and OWL Lite.  This description should be as accurate as
     possible consistent with a goal of it being comprehensible to a
     majority of the community.

RDFCore: NP completeness of owl/RDF mapping

   #owlsas-rdfcore-np-complete RDFCore notes the a consequence of the
   rules for owl:equivalentClass is that distinguishing OWL DL from OWL
   Full has complexity NP complete and suggests WEBONT investigate
   whether this complexity can be reduced.
RDFCore: B-node issues

   [..] we request, that in Owl DL and Owl lite:
      a) that a b-node representing an individual may be the object of
         more than one triple
      b) that cycles of b-nodes representing individuals be allowed.

Varant: OWL and Published Subjects

   [opportunities, no real issues/comments]
McGregor: Non-global Keys

   OWL ought to include a syntax for defining non-global keys.  For
   example, suppose the classes Employee and EmployeeHistory both share
   the attribute hasSSN.  One would like to be able to assert that
   'hasSSN' is a key for instances of Employee, but not for instances
   of EmpoyeeHistory.  InverseFunctionalProperty does not permit this.
Reynolds: OWL comment - language subsets and complexity

   We wish to register a comment on the implementation complexity of
   the selected subsets of OWL - Lite and DL - based on our
   implementation experience with Jena.

   One means to simplify OWL/Lite would be to restrict class
   definitions to only be "partial". Our concern is that this would go
   too far - there is value in having complete definitions in order to
   support classification of individuals based on their properties. We
   wonder if a constraint of the form "each classId may only
   participate in a single axiom of the form Class(classID complete
   ...)" would remove this source of complexity. We ask those with
   greater knowledge of this field to explore whether an approach along
   these lines would enable OWL/Lite to better live up to its name.
Merry: OWL Comment: have long CR period for OWL, or move owl:oneOf, owl: have
Value to OWL Full

   An alternative, would be to redefine OWL DL downwards, excluding
   owl:oneOf and owl:hasValue, which would then be subject to the
   health warnings of OWL Full - i.e. use of these constructs means
   that your ontology is likely to be outside the limits of practical
   reasoning. Such a redefinition of OWL DL, could sensibly accompany a
   redefinition of OWL Lite to exclude complete class definitions.
OWL comment - blank nodes in OWL DL

   It is not clear why OWL DL has not permitted, for example, an
   unnamed individual to be the object of more than one triple, or an
   unnamed individual to be the object of a triple of which it is the
   subject.  Please either relax this constraint or offer a rationale.

Beckett: OWL S&AS comment - owl:imports
See also Use case raised by Golbeck

   A semantic import mechanism for the RDF-based languages looks
   potentially useful and in considering if and how to implement it,
   there are some problems.

   Firstly it seems that owl:imports potentially will import the entire
   semantic web of OWL Ontologies.  Have you considered the security
   and denial-of-service implications of this mechanism?

   Secondly, is not clear at what stage that this (Imports Closure
   http://www.w3.org/TR/2003/WD-owl-semantics-20030331/rdfs.html#5.3 )
   should be done.  In an example where you have some RDF/XML that will
   map to RDF triples describing an OWL ontology, what are the steps
   that you expect to happen?

   use case: NCI cancer ontology - wants to break into smaller pieces, but
   import rebuilds the whole thing.

Beckett: OWL Reference comment - RDF Schema for OWL

   > Appendix B is not normative.

   So that means there is no normative description in machine readable
   form of the OWL vocabulary, in OWL, as written down in RDF/XML.  Is
   all the OWL vocabulary expected to be built-in application
   knowledge?  What is the purpose of this section?  It would benefit
   from an explanation.
Beckett: OWL S&AS: Translation to RDF Graphs

[only S&AS?!]

   This transformation table gives the mapping from OWL's abstract
   syntax to RDF triples which means that if you have an OWL ontology
   in the abstract syntax you can write it in OWL's transfer syntax -
   RDF triples.

   It is however more difficult to see how to go from RDF triples to
   OWL's abstract syntax.  As a semantic web technology, OWL builds on
   RDF triples (and RDF on XML for syntax, URIs etc.) and this form of
   presentation makes it harder to see how to start with RDF and gain
   from OWL vocabulary.

wwmm:  AllDisjoint 

see also: support from Vatant and McCullough
Alford: AllSame
2003May/0070.html see also: Use case raised by biologists
(reported by Hendler)
http://lists.w3.org/Archives/Public/www-webont-wg/2003May/ 0206.html

   Since there is an owl:AllDifferent, why is there not an
   owl:AllDisjoint?  It means that all class disjoint with each

   use case: biological taxonoma with 100s of disjoint classes
   at some levels. Note this is NOT a disjoint union, just a
   large set of disjoints.
Laskey: General issues

   I have been thinking about the OWL Last Call drafts for some
   time and I have been troubled by a general feel of unease.
   While the use cases provide a broad range of interesting and
   useful scenarios, my general feeling is that OWL as
   presented will not be an effective means to accomplish these
   ends.  I would be more comfortable if I could point to
   specific shortcomings that I could suggest be corrected
   (such as the n^2 problem with disjoint classes - why not
   have a mutuallyDisjoint construct that is applicable to a
   list of arguments?), but my issues go deeper than this.  In
   discussions with others (including some outside SAIC), I
   have encountered a pervasive feeling that OWL might be
   interesting but will not have significant impact on real
   problems.  Any examples in the drafts that go beyond the
   trivial are complicated and tedious, and it is unlikely that
   anyone beyond a diehard would have the motivation to do any
   significant ontology capture in this format.

Received on Thursday, 15 May 2003 19:09:10 GMT

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