xml-dev - Comparing PUBLIC identifiers for equality.

[Alan Kennedy <alank@xhaus.com>]

Hello all,

I am working on a repository application, which needs to carry out
comparison of SYSTEM, PUBLIC and Namespace identifiers. I'm trying
to figure out how to deal with PUBLIC identifiers, and I'm wondering
about the following

 o Are PUBLIC identifers guaranteed to be unique? For example,
if the PUBLIC identifier "-//W3C//DTD HTML 4.0 Transitional//EN"
is used, can different people legally use that identifier to refer
to different things? I suppose another way of stating this question
is "How are people's catalog databases populated?"

 o Is there a repository or management body for well-known
PUBLIC identifiers?

 o Is there a standard structure/grammar which I can use to
decompose PUBLIC identifiers? 

If PUBLIC identifiers are globally unique, and always refer to the
same thing, then obviously (?) I can just do a simple string
comparison to see if they are equal.
 
TIA for any enlightenment.

Alan.