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   Re: SAX: two alternatives for namespaces

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  • From: John Cowan <cowan@locke.ccil.org>
  • To: XML Dev <xml-dev@ic.ac.uk>
  • Date: Wed, 29 Jul 1998 09:55:02 -0400

David Megginson wrote:

>   What changes to SAX 1.0 are required to support two-part names?

Follows a summary of my views.

> 1. Concatentation
>   Use a single Java String (or C++ wstring, etc.) to represent a
>   two-part name; select a non-XML character to use as the separator.

I strongly support this.

>   Advantages:
>   - requires no modification to SAX 1.0

Also: it can be layered on top of existing SAX-compliant parsers
as a filter, so that parsers need not change for namespace support.

>   Disadvantages:
>   - places additional burden on applications
>   - may produce unexpected results with applications that assume only
>     traditional one-part names (especially normalisers)

Adding namespace support in a filter makes avoiding these problems
easy: if namespace interpretation is a Bad Idea for your application,
don't install it.  It is applications, not parsers, that need or
don't need namespace information.

>   - makes equality testing tricky

I'm not sure I understand this.  Assuming that all relative URLs are
coerced to absolute form (which my current implementation regrettably
does not do), there seem to be no special issues.
> 2. New Interface

>   Advantages:
>   - provides easy and separate access to the URI part and the base
>     part of a name

Adding a few static routines to separate a combined string into its
components adds very little space cost, though admittedly some
runtime cost.

>   Disadvantages:
>   - backwards-incompatible with SAX 1.0; all software would have to
>     change

I think this is a very large cost indeed.
> Of course, we should finalise nothing until the namespaces spec
> becomes a recommendation.

Agreed, but experimental implementations are well worthwhile.
John Cowan	http://www.ccil.org/~cowan		cowan@ccil.org
	You tollerday donsk?  N.  You tolkatiff scowegian?  Nn.
	You spigotty anglease?  Nnn.  You phonio saxo?  Nnnn.
		Clear all so!  'Tis a Jute.... (Finnegans Wake 16.5)

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