SAX2 Namespace Support
cox_andy at bah.com
Wed Jan 5 16:34:12 GMT 2000
The semantics of operator==() and equals() should match the concept that the
If I understand the Namespaces spec  correctly, an identical URI (defined
in the spec as "exactly the same character-for-character") and an identical
local part imply an identical QName. According to the spec, "the prefix
functions only as a placeholder for a namespace name." 
The URI is the key. Even in the intro, the authors emphasize that the XML
version of namespaces "is not, mathematically speaking, a set."
One man's opinion...
| -----Original Message-----
| From: owner-xml-dev at ic.ac.uk [mailto:owner-xml-dev at ic.ac.uk]On Behalf Of
| Leigh Dodds
| Sent: Wednesday, 05 January 2000 10:47 AM
| To: David Megginson
| Cc: xml-dev
| Subject: RE: SAX2 Namespace Support
| > In principle (the principle of least surprise), it's very bad
| > behaviour for two objects to be == in C++ or equals() in Java if any
| > of their publicly-accessible fields differ. Think of sets, for
| > example.
| In this instance though your level of surprise is going to relate
| to how familiar you are with the Namespaces spec. After reading
| it I'd be surprised if two QNames with the same URIs and same local
| parts aren't the considered equal.
| The problem though boils down to how often, in reality, XML instances
| will have the same Namespace declared twice, with different prefixes.
| I'd have thought this would be pretty unlikely. In a data interchange
| context standardising prefixes for Namespaces would mitigate this
| 'problem' and would probably have beneficial side-effects as well.
| In a document authoring context I can't imagine using the same
| Namespace with two prefixes, except by accident. Readibility
| (of the XML) is reduced with Namespaces anyway, sprinkling additional
| prefixes around makes this worse.
| 2-penneth worth.
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