Re: [xsl] declarative language, need for loops etc.

Subject: Re: [xsl] declarative language, need for loops etc.
From: Wendell Piez <wapiez@xxxxxxxxxxxxxxxx>
Date: Wed, 16 Oct 2002 11:52:52 -0400

No, you're not stupid, you're just climbing the hill as all of us have done.

At 06:40 AM 10/16/2002, you wrote:
In my experience as an beginner in xslt I understand slowly whats "behind" xslt as a declarative language. What I dont understand is, that there is still some "need" for iterative solutions wich is not part in the xslt.

This is true: the XSLT screwdriver is not the best tool for every job. "Iterative solutions" (by which I take it you mean an imperative approach to transformations, giving the programmer control over the flow of operation) are sometimes exactly what's called for. But they are generally not XSLT's thing.

And I have to do something like this:

Wich basic concepts is missing? What do I not understand?

You haven't said anything here that indicates a lack of understanding. Rather, it sounds as though you are developing, along with a sense of "the XSL Way", a map of the different kinds of problems that XSL is more or less good at solving.

Keep in mind that XSLT was designed with a particular range of use cases in mind:

"XSLT is also designed to be used independently of XSL. However, XSLT
is not intended as a completely general-purpose XML transformation language.
Rather it is designed primarily for the kinds of transformations that are
needed when XSLT is used as part of XSL." [XSLT Abstract]

In order to complete this picture, you need to understand that XSL specifies a formatting language (XSLFO); in other words, "the kinds of transformations that are needed when XSLT is used as part of XSL" means the kinds of transformations needed when converting XML documents -- especially (but not only) "document-oriented" XML documents -- into a presentation format; and to do so in a way that plays well with a range of deployments and architectures. Since HTML is basically a presentation format, it is a (very) popular alternative to XSLFO as a target language for XSLT transformations, and XSLT generally works well with it.

What XSLT is not designed for, however, is arbitrary transformations such as one might have in an information-processing pipeline before that "terminal" stage of creating formatted output. Since it is well-designed, XSLT can nonetheless often be pulled into service for many such transformations, although a number of features one might like in such a language are missing from XSLT.

Whether XSLT is well-suited to your problems partly depends on how well your problem fits the kinds of transformations for which XSLT is designed. There are other kinds of transformations too. Readers of this list are used to pushing the boundaries with XSLT (hence Oliver's loop-compiler, for example) -- but it's still not a panacaea.

I hope that helps,

====================================================================== 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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