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Re: semantics and RDF(S)

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Fri, 12 Jan 2001 14:21:40 -0500
To: fikes@KSL.Stanford.EDU
Cc: www-rdf-logic@w3.org
Message-Id: <20010112142140R.pfps@research.bell-labs.com>

Perhaps a metaphor for the situation as Richard and I see it might be
useful here.  We both see the glass as 90% full in the sense that there is
a good start and there is enough to support at least non-controversial uses
of DAML+OIL.  

However, I believe that we have got 90% of the way with somewhat less than
10% of the effort.  I believe that there are lots of serious problems
remaining and that coming up with meaning for the rest of RDF and RDF
Schema will be extraordinarily difficult.  Moreover, I believe that most
uses of DAML+OIL will want to use some of the parts of RDF and RDF Schema
that do not have a firm meaning.  Thus, although one way of measuring
progress is that we are 90% done, another way is that we are only 10%
done, as only 10% (or so) of the DAML+OIL ontologies will use only the
well-specified parts of RDF and RDF Schem.

As a good example of the difficulties that will be encountered, consider
whether the following DAML+OIL ontology is consistent.

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-schema-ns#"
	 xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
         xmlns:daml="http://www.daml.org/2000/12/daml+oil#"
	 xmlns="#">

<rdf:Property rdf:ID="#bar"/>

<rdfs:Class rdf:ID="foo">
  <rdfs:subClassOf>
    <daml:Restriction daml:cardinality="1">
      <daml:onProperty rdf:resource="#bar"/>
    </daml:Restriction>
  </rdfs:subClassOf>
</rdfs:Class>

<rdf:Bag rdf:ID="#bag1>
  <rdf:li rdf:resource="#bag1">
<rdf:Bag>

<rdf:Bag rdf:ID="#bag2>
  <rdf:li rdf:resource="#bag2">
<rdf:Bag>

<foo>
  <bar rdf:resource="#bag1"/>
  <bar rdf:resource="#bag2"/>
</foo>

</rdf:RDF>


Peter Patel-Schneider
 
Received on Friday, 12 January 2001 14:22:01 GMT

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