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RDF-WordNet: representation issues

From: Guus Schreiber <schreiber@swi.psy.uva.nl>
Date: Wed, 26 Jun 2002 15:10:23 +0200
Message-ID: <3D19BD3F.A9CC89E8@swi.psy.uva.nl>
To: www-rdf-interest@w3.org
CC: Stefan Decker <stefan@db.stanford.edu>

Exploiting corpora such as WordNet and the Art and Architecture
Thesaurus is (at least from our perspective) essential for making the
vision of a semantic web come true. In practice however, using an RDF
representation of WordNet poses a number of problems. 

We are currently looking at the (unofficial) RDF-WordNet developed by
Sergey Melnik and Stefan Decker [1].  They provide an RDF Schema with
class definitions for "LexicalConcept" (i.e. a synset) and its
subclasses (noun, verb, ...). as well as property definitions for
"wordForm" (synset -> term), "glossaryEntry" (synset -> description) and
"hyponymOf (synset -> synset). The WordNet corpus itself is represented
as RDF files with instances of these schema definitions.

One  disadvantage of this representation is that the WordNet hierarchy
is now "hidden" in the hyponymOf triples. One could therefore argue that
this representation is wrong. However, if the semantic web really
becomes a reality, different representation choices will be a fact of
life. So, we looked at a neat way of defining our interpretation of
"WordNet as a class hierarchy" as an add-on RDF Schema. It turned out
that with two definitions we could solve this problem:

1. wn:LexicalConcept rdfs:subClassOf rdfs:Class
2. wn:hyponymOf rdfs:subPropertyOf rdfs:subClassOf
In addition, we included:

3. wn:wordForm rdfs:subPropertyOf rdfs:label
4. wn:glossaryEntry rdfs:subPropertyOf rdfs:comment

which also seems to make sense. See [2] for the RDF Schema file. 

Although it first seemed like a hack, on second thought this might
actually be a decent way to do this kind of ontology/representation
mapping. Note that this approach makes heavy use of RDF's metamodelling

Comments/suggestions are very welcome,

Guus Schreiber

P.S. This work is done in the context of research on semantic image
annotation and search [3]. Up till now, we are using our own RDF-WordNet
conversion. However, for realistic applications we believe we should use
as much as possible publicly available web resources (and solve the
resulting representation mapping problems).  

[1] http://www.semanticweb.org/library#wordnet
[2] http://www.swi.psy.uva.nl/usr/Schreiber/schema/wnclass.rdfs
[3] http://www.swi.psy.uva.nl/usr/Schreiber/papers/Schreiber01a.pdf

A. Th. Schreiber, SWI, University of Amsterdam, Roetersstraat 15
NL-1018 WB Amsterdam, The Netherlands, Tel: +31 20 525 6793 
Fax: +31 20 525 6896; E-mail: schreiber@swi.psy.uva.nl
WWW: http://www.swi.psy.uva.nl/usr/Schreiber/home.html
Received on Wednesday, 26 June 2002 09:27:29 GMT

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