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Re: [ontolog-forum] OWL and lack of identifiers

To: <edbark@xxxxxxxx>, "[ontolog-forum] " <ontolog-forum@xxxxxxxxxxxxxxxx>
From: "Peter F Brown" <peter@xxxxxxxxxx>
Date: Mon, 16 Apr 2007 20:58:38 +0200
Message-id: <1B2253B0359130439EA571FF30251AAE02573F@xxxxxxxxxxxxxxx>
"The problem with this approach is that you don't get a mnemonic URN 
identifier; you get a digit string.  People won't be able to remember or guess 
these things, and IANA hasn't yet thought about check digits for the 9-digit 
numbers that they will need if every business in the world registered one.  So 
we have yet another number that functions like a telephone number, without the 
very valuable advantage of cascading directories.  As designed, URNs are one 
giant telephone book with an unbounded list of numbers that might well hit 
10**10."    (01)

This is not, or should not be a problem: we shouldn't confuse identity and 
identifier: a URN provides the latter, presumably unique, in such a way that 
you can make an assertion about the identity of the "thing" identified, or - in 
more formal FOL terms - assert the identity (in the formal "equals" sense) of 
"thing a" and "thing b" [1], because they have the same identifier.    (02)

On its own an identifier is no more than a "handle". As a "best practice" you 
should *not* put any semantics in a unique identifier if you want to stay out 
of trouble, even if some people do, and can, make certain inferences from 
parsing the string that "is" the identifier.... BTW, in respect to an earlier 
posting, an ISBN does not identify a book, but the edition of a book - hardback 
and softcover, different editions, translations, etc all carry different 
ISBN's: it is not the identifier of the "work" (as in "opus").    (03)

Peter    (04)

[1] With due apologies to Dr Seuss's Thing One and Thing Two... ;-)    (05)

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