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

To: patrick@xxxxxxxxxxx, "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: "John F. Sowa" <sowa@xxxxxxxxxxx>
Date: Sun, 15 Apr 2007 12:46:52 -0400
Message-id: <462256FC.2020400@xxxxxxxxxxx>
Patrick,    (01)

 > Yes, but would you agree that there is no one
 > universal space-time coordinate system such that
 > any physical object could have two or more unique
 > identifiers in different coordinate systems?    (02)

There is no problem with having multiple naming systems
if there is a one-to-one mapping between them.    (03)

For example, there's a one-to-one mapping between
rectangular coordinates (x,y,z) and polar coordinates
with a radial distance r and two angles (assuming, of
course, that you treat angles modulo 360 degrees as
identical).  For some applications, one coordinate
system might be better than the other, but you can
always transform one system to the other.    (04)

But there are many issues about systems for which
there is no unique mapping and for which there is
no clear idea of what exactly is being identified.    (05)

For example, a URI that points to a location uniquely
identifies that location.  But what happens with the
following cases:    (06)

  1. The contents at that location change over time.    (07)

  2. The contents move to another location.    (08)

  3. The contents are identical to the contents at
     many other locations.    (09)

  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?    (010)

Similar problems occur with most other naming systems,
but they become especially difficult when you're talking
about abstract stuff like information.    (011)

John    (012)

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