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

Subject: RE: [xsl] XSLT/XPath 2.0 (was "Identifying two tags...")
From: Wendell Piez <wapiez@xxxxxxxxxxxxxxxx>
Date: Mon, 13 May 2002 17:39:43 -0400

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?


====================================================================== Wendell Piez mailto:wapiez@xxxxxxxxxxxxxxxx Mulberry Technologies, Inc. 17 West Jefferson Street Direct Phone: 301/315-9635 Suite 207 Phone: 301/315-9631 Rockville, MD 20850 Fax: 301/315-8285 ---------------------------------------------------------------------- Mulberry Technologies: A Consultancy Specializing in SGML and XML ======================================================================

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