Re: result documents in an XSLT step?

On 02.11.2020 18:41, David Birnbaum wrote:

> For future reference, though, I'd be grateful for the opportunity to
> confirm the source of my misunderstanding of how to use <p:filter> — not
> only my failure to use a wrapper (I understand why that's important),
> but why it requires curly braces inside single quotation marks inside
> the double quotation marks around the value of the @select attribute. By
> way of attempting my own explanation: The spec at
> https://spec.xproc.org/master/head/steps/#c.filter says that @select on
> <p:filter> is a string, and that "the select expression is computed
> dynamically." Meanwhile, the other spec at
> https://spec.xproc.org/master/head/xproc/#p.with-input says that @select
> on <p:with-input> is an XPath expression. I think my mistake was
> assuming (instead of checking the spec carefully) that the value
> of @select would always and everywhere be an XPath expression, as (I
> think) it is inside XSLT wherever it is part of the signature of an
> element in the XSLT namespace. If it is a string, though, I need to
> dereference the string value of $current-paradigm, put it in quotes, and
> use that as one of the comparands inside the predicate, and the literal
> single quotes become the quotes around the string value and the curly
> braces inside them serve the usual AVT function of interpreting the
> XPath expression in place.

I will leave the explanation to the XProc guys but as for your
description and the difficulties to understand the difference, I think,
if you don't already have it, consider to get Erik Siegel's book on
XProc 3 (XProc 3.0 Programmer Reference), he has a section explaining
when XPath expressions are evaluated by the pipeline and when they are
evaluated by the step itself.

In general I think his book is very helpful to serve as an introduction
to a user of XProc 3, better than the specs which by their nature are
too formal and more geared towards implementors.

Received on Monday, 2 November 2020 18:56:29 UTC