I think there are very good reasons for keeping the pipeline layer separate
from the components that are integrated within the pipeline.
One reason is that XSLT modules are not very modular; when you combine them
using include and import, this can cause all sorts of unexpected effects due
to the fact that templates and variables have global scope. (This is the
main reason that XSLT processors do not generally allow modules to be
independently compiled.) For the pipeline layer you want a technology that
integrates existing stable and tested components without changing their
behaviour.
Another reason is that a product that implements the pipeline layer (I'm
thinking of Orbeon as an example) is likely to have good facilities for
configuring and debugging the pipeline that are appropriate to that level of
the system, for example giving you the ability to choose whether or not to
do validation of intermediate results between different stages of the
pipeline. It's nice not to have to build that stuff into your own code.
A typical application involves gathering data from the user, querying or
updating a database, and generating output. A good way to achieve that is to
combine the strengths of XForms, XQuery, and XSLT. XProc provides the glue
that enables these technologies to be combined in a single application.
Michael Kay
http://www.saxonica.com/
-----Original Message-----
From: Vladimir Nesterovsky [mailto:vladimir(_at_)nesterovsky-bros(_dot_)com]
Sent: 28 June 2008 17:38
To: xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com
Subject: [xsl] XProc or not XProc?
Hello!
In the project I'm working on, I've found myself performing
tasks XProc was designed for.
Namely perfroming a series of transformations, according to a
configuration, with massive input, and output, and with error
handling.
To achieve a desired effect I had to create a set of
extension function.
And now, I have questions:
Is XProc so really required?
Why should XProc be designed rather than extending (providing
new api for) xslt/xquery to perform pipeline processing?
Are xslt/xquery less declarative than XProc?
I wouldn't probably asked such questions if XProc were
already well established with implementations available.
--
Vladimir Nesterovsky
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