Re: [Use Case] ETRI-UC1: Filling the holes of OWL ontology

Gents - this issue of Uncle does go, as Chris says below, to intent. 
And it gets us into open vs. closed reasoning in a nice way - so I 
will continue it here, even though we're diverging from a use case, I 
think it is important for the eventual OWL to RIF document that we 
have some of this stuff straight.

Here's a little OWL document which defines Uncle and some family relationships

=====
Uncle a owl:class;
   rdfs:subclassOf :male;
    owl:equivalentClass
       [a owl:restriction;
          owl:onProperty :sibling;
          owl:someValuesFrom :Parent].

Parent a owl:class;
   rdfs:subclassOf :Person;
   owl:equivalentClass
   [a owl: restriction;
         owl:onProperty :hasChild;
         owl:minCardinality 1].

:Bob a :uncle;
:Mary a :Parent;
:Mary :hasChild :Amy;
:Bob :sibling :Mary;
===========
This document is consistent (I tested an XML/RDF version of it with 
Pellet, an OWL DL reasoner, I may have made minor transcription 
errors in my N3).

If I had a class called "NotUncle" which was equivalentTo the 
complement of Uncle, and asserted

:Bob2 a :male.
:Bob2 :sibling :Mary2.
:Mary2 :hasChild :Amy2.
:Bob2 a NotUncle.

then this is unconsistent (i.e. Pellet appropriately  recogizes that 
Bob2 must be an uncle and a nonUncle, which is inconsistent)


Suppose instead of "Mary a Parent" I said "Mary a NoChildrenPerson" 
(with the obvious semantics) and I left out amy, then this would NOT 
be an inconsistent document, because Bob may have other siblings.  If 
I had an onlySibling property (make it a subclass of subling that is 
both functional and inversefunctional, for example) then the above 
definitions of Uncle and Parent with the facts

:Bob a :uncle.
:Bob :onlySibling :Mary.
:Mary a :NoChildrenPerson.

Would, I believe, be inconsistent (again, apologies if I got details wrong)


Note, however, that 'm reasoning about the Class Uncle, and not the 
"uncleOf" property.  What OWL doesn't provide is a facility to say
  uncleOf(x,z) := Male(x), Sibling(x,y), hasChild(y,z)
by directly composing the properties.  However, that is far different 
from saying OWL cannot define "uncle" as did the original message
  -JH
p.s. Providing more general composite properties for OWL strikes me 
as a good use case of a RL, but not necessarily of a RIF...



At 13:58 -0500 12/12/05, Christopher Welty wrote:
>You can't do "uncle" in OWL-DL in the sense you want, I think Jim's point
>was that you can define *something* that eliminates some unintended
>models.  Unless one of the mindlab guys have found another clever b-node
>based trick.
>
>-Chris
>
>Dr. Christopher A. Welty, Knowledge Structures Group
>IBM Watson Research Center, 19 Skyline Dr., Hawthorne, NY  10532
>Voice: +1 914.784.7055,  IBM T/L: 863.7055, Fax: +1 914.784.7455
>Email: welty@watson.ibm.com
>Web: http://www.research.ibm.com/people/w/welty/
>
>
>
>Bill Andersen <andersen@ontologyworks.com>
>Sent by: public-rif-wg-request@w3.org
>12/12/2005 06:42 AM
>
>To
>Enrico Franconi <franconi@inf.unibz.it>
>cc
>Jim Hendler <hendler@cs.umd.edu>, Minsu Jang <minsu@etri.re.kr>, W3C RIF
>WG <public-rif-wg@w3.org>
>Subject
>Re: [Use Case] ETRI-UC1: Filling the holes of OWL ontology
>
>
>
>
>
>
>
>Hi all,
>
>Enrico, thanks for clarifying the issue on tree-shaped models.
>
>Jim, could you provide a reference (or perhaps an example) to how one
>does "uncle" in OWL-DL?
>
>Thanks,
>
>                  .bill
>
>On Dec 12, 2005, at 04:27 , Enrico Franconi wrote:
>
>>
>>  On 11 Dec 2005, at 18:39, Jim Hendler wrote:
>>>  At 19:57 +0900 12/11/05, Minsu Jang wrote:
>>>>  When building ontologies using OWL, we usually come up with such
>>>>  relations or classes that are difficult or impossible to express
>>>>  in OWL, which creates vocabulary holes in the ontologies. The
>>>>  most representative hole is the set of relations that can be
>>>>  defined by chained properties[1][2]. For example, with OWL alone,
>>>>  you cannot describe "uncle" relation, which is the composition of
>>>>  "father" and "brother" relation, into the family ontology. With
>>>>  rules, it's trivial to describe the relations defined by chained
>>>>  properties. As such, RIF will be an essential semantic web
>>>>  language that complements and extends OWL.
>>>
>>>  Actually, let us be clear here - it is easy to come up with a
>>>  definition of uncle in OWL and one can even rule out inconsistent
>>>  cases using a DL reasoner (for example,  I could discover it was
>>>  inconsistent for Bob to be in a "no siblings" class if I knew Bob
>>>  was in the uncle class).  What each of the various approaches can
>>>  do with "uncle" is actually quite complicated, gets into issues of
>>>  grounded literals and other such things (i.e. many rule systems
>>>  can't find all uncles because you may need unsafe reasoning to
>>>  remain decidable) -- I don't object to the thrust of the use case
>>>  about doing things OWL cannot, but this canard about "not doing
>>>  uncle" is a misunderstanding of something Ian Horrocks said in
>>>  some email to the Web Ontology Working Group (i.e. it's been taken
>>>  out of context)  and needs to be much more carefully elucidated if
>>>  you want to use it in a use case...
>>
>>  I guess that a proper use case could be built on the fact that
>>  nominal-free OWL-DL does not have the ability to describe non-tree
>>  models: you need to extend the language, e.g., with rules, to be
>>  able to *properly* describe cyclic graph shaped models.
>>
>>  cheers
>>  --e.
>>
>>
>
>Bill Andersen (andersen@ontologyworks.com)
>Chief Scientist
>Ontology Works, Inc. (www.ontologyworks.com)
>1132 Annapolis Road, Suite 104,
>Odenton, MD 21113
>Office: 410-674-7600
>Cell: 443-858-6444
>Fax: 410-674-6075

-- 
Professor James Hendler			  Director
Joint Institute for Knowledge Discovery	  	  301-405-2696
UMIACS, Univ of Maryland			  301-314-9734 (Fax)
College Park, MD 20742	 		  http://www.cs.umd.edu/~hendler
(New course: http://www.cs.umd.edu/~hendler/CMSC498w/)

Received on Tuesday, 13 December 2005 02:45:43 UTC