xml-dev - Re: Identity

[David Brownell <david-b@pacbell.net>]

John Cowan wrote:
> 
> David Brownell, in a message I've unfortunately purged, thinks
> that identity is a hard concept.
> 
> Actually, it isn't.   What's hard is *determining* identity.

Which I see as part of what "identity" is ... I think that a
lot of the problems come from attempting to separate parts of
that problem.  If you can't determine the identity of this
message, what makes you sure you understand what its identity
really is?


> It took the human race millennia to determine the identity of
> the evening star with the morning star (they are identical
> with each other and with the planet Venus).

When you talk about physical objects (stars, sheep) identity
becomes a lot more concrete; easier to deal with since there's
something intrinsic (physical nature) that seems easily grasped
in at least some ases (not stars :-).  The Scarlet Pimpernel was
not the same person as the king.


>	  The labels he calls
> "extrinsic" are an attempt to bypass this problem.

Not at all.  "Who is the President?"  Presidency is an extrinsic
attribute, a label that refers to different things in different
contexts.  Much like (drum rull) a URI refers to something, and
that something often changes over time.

Consider that one of the oft-stated characteristics of computer
systems is the ability to create "identical" (sic) copies.  Hmm.
Does that mean the copies share the same "identity"?  Not in
terms of intrinsic identity, clearly.  Extrinsically, you can
rename them to take whatever identity pleases you.

- Dave

p.s. The Extrinsic/Intrinsic distinction is one I first found in
	an OODB paper from somewhere in Texas.  The database folk
	were having a hard time of this one, and concluded it was
	because all they had to work with were "extrinsic" notions
	and they were treating them like "intrinsic" notions.

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