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

To: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: "John F. Sowa" <sowa@xxxxxxxxxxx>
Date: Sun, 15 Apr 2007 19:09:08 -0400
Message-id: <4622B094.4010009@xxxxxxxxxxx>
Waclaw,    (01)

To begin with the conclusion:    (02)

JFS>> Similar problems occur with most other naming systems,
 >> but they become especially difficult when you're talking
 >> about abstract stuff like information.    (03)

WK> Yes, and this is why the assumption behind semantic web
 > technologies that a URI should identify the same entity
 > on every occasion should be treated with highest suspicion.    (04)

That is the problem.  People need a content identifier, but
what they are given is a location identifier.    (05)

Some further comments on the preceding four points:    (06)

JFS>> For example, a URI that points to a location uniquely
 >> identifies that location.  But what happens with the
 >> following cases:
 >> 1. The contents at that location change over time.    (07)

WK> I would say: nothing happens. If the URI points to a
 > location (given some arbitrary system of coordinates),
 > the change of the content of the location does not change
 > the location.    (08)

That's the problem:  nothing happens.  But more often
than not, the person who is looking for the information
needs to know (a) whether the content has been changed,
(b) why it has been changed, or (c) where the original
information can be found.    (09)

JFS>> 2. The contents move to another location.    (010)

WK> See above.    (011)

Yes, all the problems of #1 are repeated.    (012)

JFS>> 3. The contents are identical to the contents at
 >>       many other locations.    (013)

WK> Weird; what sort of identity do you have in mind?
 > Indiscernibility?  Relative identity?    (014)

Not weird at all.  Indiscernible copies are abundant
throughout the WWW, deliberately, accidentally, or
illegally.    (015)

JFS>> 4. The contents can be interpreted in many different
 >>       ways -- e.g., does the URI identify a web page or
 >>       the service supported at that web site?    (016)

WK> But here clearly you mean a URI that identifies the
 > content of a region, not the region.  These should not be
 > confused.    (017)

That's what I was trying to say.  They are very commonly
confused.  What most people want is the content, but what
they are given is a location whose connection with the
content is tenuous at best.    (018)

John Sowa    (019)

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