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Representing anonymous individual in SemWeb Best Practice documents

From: Benedicto Rodriguez <br205r@ecs.soton.ac.uk>
Date: Mon, 15 Oct 2007 00:54:16 +0100
Message-ID: <CD0CED2DB07AA249BF8BC259CADD260C700D48@dumbledore.ecs.soton.ac.uk>
To: <public-owl-dev@w3.org>

Hello everyone,

(This post probably belongs to the public-swbp-wg-request@w3.org mailing
list, but given that the working group is now closed and the type of
questions included, I thought it would be ok to post it here instead).

Two of the documents in the SWBPD WG ([1], [2]) talk about representing
anonymous individuals as the value of a property using an existential
restriction.

[1] Representing Classes As Property Values on the Semantic Web. (See:
Approach 4). http://www.w3.org/TR/swbp-classes-as-values/

[2] Representing Specified Values in OWL: "value partitions" and "value
sets". (See: Pattern 2, variant 2).
http://www.w3.org/TR/swbp-specified-values/

In both cases only the N3 syntax for this variant is provided, not the
corresponding OWL implementation. 
According to both documents the resulting OWL implementation is within
OWL-DL expressivity. 

*** My goal is simply to write this OWL implementation within OWL-DL but
I run into some problems doing so.

A) 	I noticed that the N3 syntax provided in [1] and [2] for this
variant doesn't parse in the only N3 validator online I found
(http://rdfabout.com/demo/validator/ listed in the SemanticWebTools page
of the ESW Wiki). 

Now, I'm not sure if this is because the N3 syntax is actually NOT
correct or because of an issue with the parser. (?)

In [2] for example. To parse this variant I used the file
http://www.w3.org/TR/swbp-specified-values/value-partitions-variant-1.n3
(provided in [2]) replacing the definition of :John in the file for the
definition shown below (also provided in [2]) and after a couple of
tweaks to bypass an empty relative URI issue:

### Define John as an individual of type person and of type
has_health_status someValuesFrom Good_health_status
:John
    a      :Person ;
    [    a      owl:Restriction;
         owl:onProperty :has_health_status ;
         owl:someValuesFrom :Good_health_value
    ].

B) 	The following modification to the previous N3 snippet solved the
parsing problem, but I'm not sure if this is what the original N3
expression shown in A) intended to represent (?):

:John
    a      :Person ;
    :has_health_value
        [    a      owl:Restriction;
             owl:onProperty :has_health_status ;
             owl:someValuesFrom :Good_health_value
        ].

Now, I have tried 2 options when converting the N3 snippet shown in A)
into OWL.
(Again, the original claim in [1] and [2] is the representation of an
anonymous individuals as the value of a property using an existential
restriction).

C) 	Option 1: This OWL implementation would place the model is in
OWL Full because the value of the property "has_health_status" is an
anonymous class defined by a restriction rather than an anonymous
individual. 
This deviates from the intention in [1] and [2].

<Person rdf:about="#John">
   <has_health_status>
      <owl:Restriction>
 	   <owl:someValuesFrom>
            <owl:Class rdf:about="#Good_health_value"/>
         </owl:someValuesFrom>
         <owl:onProperty>
            <owl:FunctionalProperty rdf:about="#has_health_status"/>
         </owl:onProperty>
      </owl:Restriction>
   </has_health_status>
</Person>

D) 	Option 2: This OWL implementation leaves the model in OWL-DL
because the value of the property "has_health_status" is an anonymous
individual from the class "Good_health_value". 
However it doesn't seem to correspond to the original N3 expression
given that it lacks the "someValuesFrom" restriction.

  <Person rdf:about="#John">
	  <has_health_status>
		<Good_health_value/>		
	  </has_health_status>
  </Person>

E) 	The same issues and same possible solutions apply to the
representation of :LionsLifeInThePrideBook in Approach 4 in document
[1]:

:LionsLifeInThePrideBook
      a       :Book;
      [ a       owl:Restriction ;
                owl:onProperty dc:subject ;
                owl:someValuesFrom :Lion      ];
      rdfs:seeAlso <http://isbn.nu/0736809643> ;
      :bookTitle "Lions: Life in the Pride" .

In conlusion, any suggestions of what the OWL-DL implementation of the
N3 snippet in A) should be?
Is the OWL in D) a sensible solution?

Additionally, any comments regarding what may be causing the parsing
issue of the N3 shown in A)?
Do you think the modification shown in B) (that parses OK), is what [2]
intended to represent?

Any other comments/feedback would be very welcome and appreciated.

Regards,
Bene Rodriguez

Postgraduate Student | Intelligence, Agents and Multimedia Group |
School of Electronics and Computer Science | University of Southampton |
Southampton SO17 1BJ | United Kingdom | Phone: +44 23 8059 3122 | Email:
bene@soton.ac.uk
Received on Monday, 15 October 2007 04:17:17 GMT

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