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Re: [WNET, PORT, OEP] Synset's and Classes - dumb question

From: Aldo Gangemi <a.gangemi@istc.cnr.it>
Date: Wed, 5 May 2004 16:59:18 +0100
Message-Id: <p06002009bcbeb2092fd2@[172.16.110.110]>
To: "McBride, Brian" <brian.mcbride@hp.com>
Cc: SWBPD list <public-swbp-wg@w3.org>

Hi Brian,

At 14:05 +0100 5-05-2004, McBride, Brian wrote:
>Looking through the discusion on representing WordNet, I've been trying to
>understand the relation between wordnets, thesauri and ontologies.

you can download various papers and tutorials from our site that 
explain distinctions: http://www.loa-cnr.it.
BTW, the basic issues are:

1) ontologies in the *formal* sense are axiomatic theories, while 
thesauri and wordnets are only graphs (tree structures, forests), 
whose primitives have no explicit formal semantics
2) primitives assumed in those graphs can be given a formal semantics 
by making appropriate interpretations and adjustments, therefore 
wordnets and thesauri can be transformed into formal ontologies
3) wordnets assume typical primitives coming from linguistics, while 
thesauri assume primitives coming from terminology, library 
management, etc.
4) a conservative alternative in porting thesauri and wordnets to OWL 
is considering them just "structures" (e.g. RDF models), and not 
ontologies.

>Is there a consensus view on the relationship between a wordnet synset and
>the class the synonyms names, i.e. is the synset containing the word 'dog'
>necessarily owl:sameAs the class of dogs?

owl:sameAs applies to owl:Individuals, so you are asking a meta-level 
question :)

OK, my position is that - provided that we want to transform a 
wordnet into a formal ontology - the semantic interpretation of 
"synset" is that of an equivalence class of words/terms according to 
a common intended meaning. Since "having a unique intended meaning" 
is also applicable to classes, the *default* mapping of synsets is to 
owl:Class.
On the other hand, not only classes have a unique intended meaning, 
but also individuals, and as a matter of fact, many synsets refer to 
individuals like "Italy" or "Cicero". That's why "synset" hasn't a 
precise mapping to formal ontologies. Then, your dog example is 
correct, but not "necessarily".

>Also, does WordNet have synsets for relations?  Do such synsets have
>hypernyms or hyponyms?  If so is rdfs:subClassOf rather rdfs:subPropertyOf
>correct?
>

WordNet does not distinguish explicitly synset "types". Some of them 
(specially some verbs) can be  considered as potential 
owl:ObjectProperty, and obviously have hypernyms or hyponyms.
But I do not encourage this kind of investigation, since for each 
owl:ObjectProperty you can get an owl:Class that reifies it, and this 
is what natural languages do often. E.g., is "GIVE" (as a 
verb-synset) more mappable to an owl:Class (being an action), an 
owl:ObjectProperty (someone gives something), or some OWL-DL 
construct that implements an n-ary relation (someone gives something 
to someone else in a certain way, etc., see Natasha's draft)? We have 
good motivations for each of those interpretations.

My suggestion is to map any WordNet synset to either an owl:Class or 
to an owl:Individual. owl:ObjectProperty instances should be provided 
on other grounds, for example:

a) some "lexical relations" already in WordNet as such, like meronymy 
and troponymy
b) external sources, like core ontologies
c) some synsets, used as heuristics
d) ontology learning techniques

hmm, I stop here, since what I am saying will be part of the report 
to be delivered next week.
BTW, there seems to be here a nice overlap between [WNAT] (and 
[PORT]), and [OEP], because the interpretations I have given about 
wordnets and thesauri can be considered preliminary sketches for 
ontology "reengineering" patterns, which can be a subclass of 
ontology desing patterns.

Cheers
Aldo
-- 



*;*;*;*;*;*;*;*;*;*;*;*;*;*;*;*;*;*;*;*;*;*
Aldo Gangemi
Research Scientist
Laboratory for Applied Ontology, ISTC-CNR
Institute of Cognitive Sciences and Technologies
(Laboratorio di Ontologia Applicata,
Istituto di Scienze e Tecnologie della Cognizione,
Consiglio Nazionale delle Ricerche)
Viale Marx 15, 00137
Roma Italy
+3906.86090249
+3906.824737 (fax)
mailto://a.gangemi@istc.cnr.it
mailto://gangemi@acm.org
http://www.loa-cnr.it
Received on Wednesday, 5 May 2004 11:07:08 UTC

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