SAX2: summary of Namespace-support arguments
jjc at jclark.com
Sun Dec 19 06:27:23 GMT 1999
Tim Bray wrote:
> At 12:22 PM 12/18/99 -0500, David Megginson wrote:
> >#3 (James Clark)... James would like to create a new Name class that
> > includes the
> > original prefix (if any) as well as the Namespace URI and local name.
> Actually, you are slightly mis-characterizing James' position. I don't
> think he cares about which prefix was actually used on any particular
> name, but he wants APIs to manifest the prefix/namespace mapping so that
> they can be used in things like XPath expressions.
I do indeed want that, and in the past I've argued against *requiring*
processors to provide information about the prefix used. I've become a
lot less negative about this prefix information recently and I think
it's better for an API to provide it. My reasons are:
1. I view namespaces as much more core to XML than DTDs. I want to be
able to build namespace processing into the parser at very low-level (so
it has negligible overhead); but I don't want to build XML 1.0
validation in. This means I need an API that is both namespace aware
and allows XML 1.0 validation (which of course requires prefix) to be
layerd on top of it.
2. DOM Level 2 needs prefixes. It would be very unfortunate if SAX 2
was such that DOM Level 2 could not be layered on top of it.
3. I want to use DocumentHandler not just an interface between a parser
and an application but between an application and a serializer.
Serialization can in fact be as performance critical as parsing. A
serializer can do it's job much more efficiently and easily if it has
the prefix available rather than having to figure it out from the
prefix/namespace bindings in effect. Although the combination of XML 1.0
DTDs and namespaces is a problematic, many users want to use namespaces
and still have their documents been XML 1.0 valid; this may apply to the
documents they are creating with a DocumentHandler. For a serializer
that uses a DocumentHandler as its interface to be able to do this, it
has to have prefix information.
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