RE: [xsl] XSLT/XPath 2.0 (was "Identifying two tags...")

[Wendell Piez <wapiez at mulberrytech dot com>]

Stuart,

At 01:31 PM 5/13/2002, you wrote:
>Returning to your observation, "the dependency on the complexities of
>XML Schema gives me precious little benefit, compared with the
>headaches...", I am trying to make the case that the benefit of the
>specification making use of PSVI is that XSLT implementers can program
>to that requirement and thus produce XSLT processors that are
>interchangeable. To specify otherwise would let XSLT processor behavior
>diverge, which would spell chaos.

Humbly, I'd like to submit that this is a non-sequitur. The W3C Schema PSVI 
is not the only conceivable basis on which XSLT can be standardized. Nor 
would failing to adopt the PSVI guarantee that XSLT processor behavior 
would diverge. (This is like arguing that unless everyone learns English, 
world commerce will collapse. It's understandable from a certain point of 
view why this may seem to be the case in the present day and age; but it's 
not inevitable unless we make it so.)

XSLT is already nicely standardized on the XPath data model. XSLT is itself 
capable of introducing extra-document (and extra-schema) information to a 
transform. (In fact, if XML Schema did not give several ways to do any one 
thing, it would be feasible for XSLT 1.0 itself to query a schema to get 
this kind of information. It's because of the complexity of the Schema 
language, not the weakness of XSLT, that this isn't practical in the 
general case.)

Further, I wonder what you mean by "XSLT processors that are 
interchangeable". XSLT processors are not now interchangeable (JAXP 
notwithstanding), nor are they supposed to be. XSLT stylesheets can be 
written to be independent of the particular features of the processor, and 
so be interchangeable; largely, however, this is because what they expect 
from the parser is so minimal. (And indeed, to expect true 
interchangeability you already have to avoid functions like id() which are 
very useful in some contexts but which are dependant on a parser's 
providing a non-mandatory information item, namely an attribute type.) 
Certainly, XSLT can extend the reach of what can be achieved with 
interchangeable stylesheets by mandating a more complex, featureful 
information set; but it is not at all clear that any particular information 
set, including the W3C Schema PSVI, would hit anything close to an 80/20 
point; actually the impact on the interchangeability of stylesheets may 
well be very negative.

It's like we're all driving Model T Fords, and we're being told how much 
better they'll be if they can be rigged with snow-plow blades and winches. 
You're saying if we don't all have the same blades and winches, chaos will 
result. Some of us are saying, "huh"?

But it may be that the killer application isn't the car, which is still 
fairly primitive, but the internal combustion engine. Eventually we'll be 
able to have snow plows, wreckers and the rest: that's great. But do I 
really have to have a winch on my jalopy?

Regards,
Wendell




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Wendell Piez                            mailto:wapiez@mulberrytech.com
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