Schema Processing (was Re: Fw: Namespaces)

Simon St.Laurent simonstl at
Thu Feb 4 15:15:07 GMT 1999

At 06:42 PM 2/4/99 +0700, James Clark wrote:
>> One would of course have
>> to pass the DTDs (or other schema files) through the same transformation.
>Why? DTDs are used only at the pre-transformation stage. I would expect
>a future XML Schema language to operate purely on the
>post-transformation tree.

This opens up a new can of worms, one we discussed during the creation of
XSchema (now DDML), but potentially an ugly one long term.

This paragraph suggests a process like:

1. Process document against DTD.
2. Resolve namespaces.
3. Process document against schema.

Which is fine, in some ways - I'd prefer to see schemas just define
structures, not content substitution (i.e., entities) - but opens up
potentially potent new layers of complexity that make the current mire of
well-formed and valid documents seem quite friendly.

Is the W3C ever going to take a look at making its specs into neat layers
instead of octopuses that sprawl across multiple levels of processing?
Namespaces wraps its tentacles around several parts of XML 1.0, and
duplication between schemas and DTDs may leave another generation of
would-be XML-ers scratching their heads at the odd ways of those
sophisticated folks writing the specs.

Linking and styling present similar delightful conundrums, and there's a
fairly large group of voices (mine included) on the XSL list calling for
that spec to be cleanly split into two pieces: transformation and formatting.

I'd rather have more small clean pieces that fit together neatly than large
chunks that need to wrap around each other to work properly.

Simon St.Laurent
XML: A Primer / Building XML Applications (March)
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