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Re: [ontolog-forum] Defining everything in terms of relations (was Charl

To: "'[ontolog-forum] '" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: "Patrick Cassidy" <pat@xxxxxxxxx>
Date: Mon, 24 Feb 2014 14:26:34 -0500
Message-id: <141e01cf3196$547198e0$fd54caa0$@micra.com>
John, I have a question about one of your comments:    (01)

 >A class is defined as a pair (t,s), where t is a monadic relation called
the type,
 >and s is the set of everything for which t is true.
 >    (02)

    It seems as though in this definition, if the relation "t" alone defines
a class, then every class must be defined by both necessary and sufficient
conditions ("the set of **everything** for which t is true").
    But In many ontologies I have seen many classes are described by only
necessary conditions.   In this case, satisfying the predicate is not enough
to be a member of the class, though being a member of the class necessarily
means that one satisfies the necessary conditions.    (03)

    Does this mean that the typical "class" in an OWL ontology is not a
"Class" in this formalism?    (04)

Comments?    (05)

Pat    (06)

Patrick Cassidy
1-908-561-3416    (07)

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