[xsl] XProc or not XProc?

["Vladimir Nesterovsky" <vladimir@xxxxxxxxxxxxxxxxxxxx>]

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