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Re: [ontolog-forum] Logic, Datalog and SQL

To: "John F. Sowa" <sowa@xxxxxxxxxxx>
Cc: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Pat Hayes <phayes@xxxxxxx>
Date: Mon, 12 Feb 2007 11:53:15 -0600
Message-id: <p06230901c1f658e4cd67@[]>
>Yes, I agree:
>  > First, you say that T is stated in terms of a nonempty
>  > vocabulary V; then you suggest that V is only a subset
>  > of the type and relation names in T.
>I was a bit hasty when I sent off that note on Jan 30th,
>and I had some second thoughts about it.  But when I
>copied it today, I had forgotten my earlier second thoughts.
>In programming languages, they distinguish variables that
>are imported by a procedure, those that are defined in a
>procedure and exported to other procedures, and those that
>are purely internal to a given procedure.  I think that
>we should make some such distinction for ontologies.
>Following is a revised version:
>     A formal ontology consists of a theory T stated in
>     some version of logic and a nonempty vocabulary V
>     of types and relations.  The names in V are divided
>     in three disjoint subsets:
>     1. Names defined elsewhere, which are used in one
>        or more axioms of T.
>     2. Names defined in T, which may be used in other
>        theories.    (01)

I would prefer that we don't say that names are "defined". Very few 
ontology languages provide for actual definitions of names, and 
several that once did (notably KIF) no longer do. Explicit 
definitions are semantically troublesome, practically of no actual 
use, create paradoxes, and generally have negative utility. The 
entire SWeb apparatus has no definitions in it anywhere, nor is it 
likely to in the future. It is very hard to even see what it would 
mean to define a globally useable name. Let us just say that names 
occur in ontologies, and ontologies constrain the meaning of names.    (02)

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