Re: [xsl] Evaluating XPath expressions found in the source document

Subject: Re: [xsl] Evaluating XPath expressions found in the source document
From: "Michael Beddow" <mbnospam@xxxxxxxxxxx>
Date: Thu, 16 Aug 2001 11:30:38 +0100
On Thursday, August 16, 2001 10:56 AM
Jeni Tennison wrote:

> No, it is an XPath expression, consisting of a single function call. I
> think that the terminology confusion comes because XPath sounds as
> though it's just about paths, but actually location paths are just one
> type of expression (albeit the most common). Expressions cover
> anything that you can put in the select attribute of xsl:value-of, so
> include arithmetic and function calls.

Hi Jeni!

So it *was* ignorance, as I suspected. But now it's replaced by deep
confusion and anxiety about the notion of a function that seems to exist
divorced from any mechanism for  implementing it (talking "functions" in
the loose computer language sense, not the mathematical one). I
understand now that those functions are part of the XPath spec, not the
XSLT spec, but surely they still have to be implemented by the XSLT
processor, and I took the query to be about implementation, not
specification.

I mean, the subset of XPath expressions I had mistakenly taken to be the
entire set are simply abstract notations of how to identify a node from
a known starting point. All they need in the real world is a possibility
of there being a instance of a tree that fits them. But concat(), though
it too is an abstraction, is one whose realisation requires a machine
somewhere that knows how to do things to the data. And where is that
machine, if not in the XSLT processor? But if that is in indeed where it
is, how is format-number() different from concat() in terms of what can
actually be done to what and where?

What struck me about the original query, as I (mis)understood it, was
that it seemed to be aiming for a LISP-like interchangeability of
programming instructions and data, which I didn't think XSLT was up to.

Sorry if my ramblings are off-topic. Perhaps they should be off-list,
too. But maybe other people are as muddled about this as I obviously am
and need the same sort of help.

Michael
---------------------------------------------------------
Michael Beddow   http://www.mbeddow.net/
XML and the Humanities page:  http://xml.lexilog.org.uk/
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