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RE: draft-rsalz-qname-urn

• To: "'Rich Salz'" <rsalz@d...>,<xml-dev@l...>
• Subject: RE: draft-rsalz-qname-urn
• From: "Michael Kay" <mike@s...>
• Date: Thu, 16 Dec 2004 13:40:33 -0000
• In-reply-to: <Pine.LNX.4.44L0.0412160721260.17310-100000@s...>
• Thread-index: AcTjak4glebionXcTAO3XOCn6PIGpAABvc0A

The spec feels a bit skimpy: there's a lot of detail missing.

For example, the semantic difference between a prefix of "" and a prefix of
"*" is left almost entirely to the reader's guesswork.

The main problem seems to be in the area of character encoding and escaping.
The abstract and introduction talk of a URN being "encoded in the same
character set as the document containing the original QName". But XML
applications cannot determine the encoding of the document. (Anyway, a
character set is not an encoding).

There's no reference to RFC2141 which defines URNs. A URN is a sequence of
characters, not bytes, so why is the encoding of the URN relevant? 

The XML namespaces rec does not require namespace names to be valid URIs.
(It sort of says they should be, but it's not an error if they aren't).
XML1.1 moves to IRIs. You therefore need to decide whether your URN format
requires the namespace name to be a valid URI, a valid IRI, or whatever.

RFC2141 requires certain characters (including %) to be %HH-escaped. If the
namespace URI already contains %HH escape sequences, will these be
double-escaped as %25HH? (If not, there is a loss of information, since XML
treats "my uri" and "my%20uri" as different namespace URIs.)

RFC2141 defines a notion of lexical equivalence, and encourages specific URN
schemes to expand on this definition. Do you intend to do so?

The XQuery specification, incidentally, defines a mapping of error QNames to
error URIs. It's different from this one, of course.

Michael Kay
http://www.saxonica.com/


> -----Original Message-----
> From: Rich Salz [mailto:rsalz@d...] 
> Sent: 16 December 2004 12:23
> To: xml-dev@l...
> Subject:  draft-rsalz-qname-urn
> 
> Some folks here may be interested in the following Internet-Draft that
> Dave Orchard and I wrote.
>   http://www.ietf.org/internet-drafts/draft-rsalz-qname-urn-00.txt
> 
> Unlike most writing on URNs and URIs, this is very short. :)
> 
> 
>     This specification defines a Uniform Resource Name 
> namespace for XML
> namespace-qualified names, QNames. As long as the URN is 
> encoded in the
> same character set as the document containing the original QName, the
> Qname URN provides enough information to maintain the semantics, and
> optionally the exact syntax, of the original name.
> 
> -- 
> Rich Salz                  Chief Security Architect
> DataPower Technology       http://www.datapower.com
> XS40 XML Security Gateway  http://www.datapower.com/products/xs40.html
> XML Security Overview      
> http://www.datapower.com/xmldev/xmlsecurity.html
> 
> 
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