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   Re: Web Resource Identity

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  • From: David Megginson <david@megginson.com>
  • To: Paul Prescod <paul@prescod.net>
  • Date: Fri, 28 May 1999 14:23:49 -0400 (EDT)

Paul Prescod writes:
 > David Megginson wrote:
 > > 
 > > But you cannot always take two references and determine if they do
 > > *not* refer to the same object -- that depends on the design.
 > "Do these refer to the same object?" => Yes/No/Maybe
 > I'm not familiar with a system like that. Can you give an example?

You will often end up with two objects that represent conceptually the
same thing but cannot be proven equivalent (two medicare records, for
example); in fact, you may even have objects that share the same set
of attributes but cannot be proven equivalent.  There's also the case
of lazy Java programmers who don't override java.lang.Object.equals()
(that represents a significant percentage of existing Java code, I'd

 > Obviously boolean logic is MUCH easier to work with than tri-nary
 > logic.

No, in the case of URLs, it's still binary:

  "Are these known to refer to the same object?" => Yes/No

And while a cononical URL is an easy extension to HTTP, the
infrastructure to support it is another issue -- do I have to
guarantee, for example, that a gzipped tar file of the same version of
the Linux kernel source at two different mirrors return the same
canonical URL?

All the best,


David Megginson                 david@megginson.com

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