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Comment on rdf:parseType="Collection"

From: Jim Hendler <hendler@cs.umd.edu>
Date: Wed, 19 Feb 2003 19:42:44 -0500
Message-Id: <p05200f66ba79d4ea39df@[10.0.1.4]>
To: www-rdf-comments@w3.org

The RDF Core Working Group documents (particularly [1]) reflect a 
decision that rdf:parsetype="collection" must be a list if RDF node 
elements.  I believe the RDF Core WG is making a mistake by 
prohibiting this from being a list of literals, and to the best of my 
ability to deduce, there is no technical reason why a list of 
literals could not be supported.

This decision has terrible ramifications for languages built on top 
of RDF (like OWL) which thus must use extremely ugly constructs for 
lists of literals (in fact, constructing the entire list using List, 
first, and rest).  For example, a natural thing to express in OWL (or 
RDFS for that matter) might be that the list of permissible scores in 
a game of tennis are 0, 15, 30, and 40.  However, instead of the 
construct

<owl:oneOf rdf:parsetype="collection">
  <score rdf:datatype="xsd:integer">0</score>
  <score rdf:datatype="xsd:integer">15</score>
  <score rdf:datatype="xsd:integer">30</score>
  <score rdf:datatype="xsd:integer">40</score>
</owl:oneOf>

we must instead


       <owl:oneOf>
         <rdf:List>
            <rdf:first rdf:datatype="xsd:integer">0</rdf:first>
            <rdf:rest>
              <rdf:List>
                <rdf:first rdf:datatype="xsd:integer">15</rdf:first>
                <rdf:rest>
                  <rdf:List>
                    <rdf:first rdf:datatype="xsd:integer">30</rdf:first>
                    <rdf:rest>
                      <rdf:List>
                        <rdf:first rdf:datatype="xsd:integer">40</rdf:first>
                        <rdf:rest rdf:resource="&rdf;nil" />
                      </rdf:List>
                    </rdf:rest>
                  </rdf:List>
               </rdf:rest>
             </rdf:List>
           </rdf:rest>
         </rdf:List>
       </owl:oneOf>

I believe the ability to express a collection of datatype values is a 
very important one, and believe it is a mistake for RDF Core to put 
this restriction on the use of rdf:parsetype="collection" without a 
stronger motivation than I can find in the current LC documents.

  thanks
  Jim Hendler
  AC Member, MIND Laboratory

p.s. Please note this is an individual comment raised as AC member, 
not a consensus comment from the web ontology working group nor does 
it necessarily represent the opinion of any other group or 
organization with which I am affiliated.  I also apologize if this 
issue has been brought up before - if it has, just consider this a +1 
for the objection.



[1] 
http://www.w3.org/TR/rdf-syntax-grammar/#section-Syntax-parsetype-Collection


-- 
Professor James Hendler				  hendler@cs.umd.edu
Director, Semantic Web and Agent Technologies	  301-405-2696
Maryland Information and Network Dynamics Lab.	  301-405-6707 (Fax)
Univ of Maryland, College Park, MD 20742	  240-731-3822 (Cell)
http://www.cs.umd.edu/users/hendler
Received on Wednesday, 19 February 2003 19:42:50 GMT

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