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xom-interest - Re: [XOM-interest] namespace checking

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Subject: XOM API for Processing XML with Java

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  • From: John Cowan <jcowan AT reutershealth.com>
  • To: elharo AT metalab.unc.edu (Elliotte Rusty Harold)
  • Cc: mike AT wyeast.net (Michael Fitzgerald), xom-interest AT lists.ibiblio.org (XOM)
  • Subject: Re: [XOM-interest] namespace checking
  • Date: Thu, 10 Oct 2002 10:29:12 -0400 (EDT)

Elliotte Rusty Harold scripsit:

> One of the reasons decision on this point was so
> tough to reach and so weak in the end was that different groups were
> going in different directions on both the meaning and use of relative
> URIs for namespace names.

On the contrary, I think everyone is now striving to avoid them. The main
reason they weren't just made illegal is that Microsoft had deployed tools
that generated them (in order to create document-local namespaces), and
some unknown number of documents already contained them. I very much doubt
whether this practice is spreading, though: people are switching to urn:uuid:
or other schemes that make uniqueness straightforward.

> The second more practical and probably solvable question is how one
> identifies an absolute URI.

A URI is absolute iff it matches this regular expression:

^[A-Za-z][A-Za-z0-9+.-]*:

See the productions "absoluteURI" and "scheme" in RFC 2396.

> The stumbling block is I can't decide if URIs containing multiple
> colons are legal; e.g. is urn:publicid:foo::bar OK?

It is entirely legal. According to RFC 3151, it is equivalent to the
public identifier "foo////bar", which is not a valid FPI but is a legal XML
public id.

See the productions "absoluteURI", "opaque_part", and "uric_no_slash" in
RFC 2396, which justify it.

(Writing RFC 3151 was a bitch. It involved carefully reconciling the
constraints of RFC 2141 (URN Syntax), RFC 2396, and ISO 9070 on FPIs.)

--
John Cowan <jcowan AT reutershealth.com> http://www.reutershealth.com
I amar prestar aen, han mathon ne nen, http://www.ccil.org/~cowan
han mathon ne chae, a han noston ne 'wilith. --Galadriel, _LOTR:FOTR_




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