RE: SWRL (FOL) n-ary relations

From: Wagner, G.R. ([email protected])
Date: 12/07/04

  • Next message: Peter F. Patel-Schneider: "comment on N-ary relations draft"
    > Can we come 
    > up with an n-ary representation that's significant simpler or 
    > otherwise better than the unary/binary SWRL representation?
    What do you mean with "significant simpler or otherwise better"?
    The issue here is simply that "objectifying" a relation may be 
    unnatural and create some undesirable (and unnecessary) overhead 
    in the language. This is not so obvious in your examples, since
    it's natural to talk about diagnoses and purchases. 
    In foundational ontology, one makes a distinction between formal
    and material relations (both of which would be represented with
    the help of predicates). In the foundational ontology GOL [1,2], 
    there is the basic assumption that material relations (such as 
    isMarriedTo/2, purchases/2, purchases/3, purchases/4) are based 
    on a "relator universal" (i.e. the intensional classes Marriage 
    and Purchase), while formal relations do not have such a basis
    and correspond to sets (extensional classes).
    If this is true, it's indeed no problem to reify material n-ary
    relations (such as "purchases/3" and "purchases/4") because there 
    is a natural class (Purchase) as the domain of n binary properties
    replacing the n-ary relation, while it will be difficult/unnatural 
    to reify formal relations suh as "between/3".
    [2]  Attached paper: G. Guizzardi1, G. Wagner, and H. Herre:     
         On the Foundations of UML as an Ontology Representation 
         Language. In E. Motta et al. (Eds.): EKAW 2004, LNAI 3257, 
         pp. 47-62, 2004.

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