xml-dev - Re: Web Resource Identity

[Paul Prescod <paul@prescod.net>]

David Brownell wrote:
> 
> There's a loose notion of "equivalence"; you can ask if
> an object reference is equivalent to another.  Primarily
> that's a syntactical operation designed to let you create
> tables keyed by object reference, without duplication; it's
> explicitly understood that the objects two references refer
> to may in fact be "the same" without having the refences be
> "equivalent".  (Some replication schemes work like that, as
> do many proxying and load balancing schemes ... large systems
> use such techniques all over the place.)

What I hear you saying is that the situation at the OMG is identical to
that in Java, Python, the ODMG and most other object-based environments.
There is a very basic notion of equivalence that you can depend upon when
you are enumerating objects at a low level. Object types can invent higher
level concepts of identity and equivalence if they want to. 

In XML, we will soon have a concept of element and attribute identity
specified by the XML Information Set. Unfortunately, the URIs that get us
to XML documents do not have the same concept. There is no way that I 
know of to declare that two URIs point to the same object. The best you
can do is say that one URI is a redirection to the other.

-- 
 Paul Prescod  - ISOGEN Consulting Engineer speaking for only himself
 http://itrc.uwaterloo.ca/~papresco

[Woody Allen on Hollywood in "Annie Hall"]
Annie: "It's so clean down here."
Woody: "That's because they don't throw their garbage away. They make 
        it into television shows."

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