Re: Issue #3306

Richard Tobin wrote:
 >> 0. Say that queries over document sequences aren't supported in XProc
 >
 > If we did this, then there is a simple workaround which is to have a
 > standard component that takes a sequence of documents and returns a
 > single document containing them as children of the root element.  You
 > can then do a query on that.

That's close from what we do in XPL right now, with the built-in
aggregate() function, but we don't find it that satisfying.

 >> 1. Say that XProc inputs and outputs are actually *sets* of documents
 >
 > Document sequences are going to be very common, as I said above I
 > think that queries on document sequences are much rarer.  We shouldn't
 > let the sequence-query tail wag the sequence dog.
 >
 > We could say that sequences decay into sets when used for pipeline
 > queries.

I think we can talk about document sequences in terms of
node-sets. This has the benefit of sticking 100% with XPath 1.0.

 >> Do people have examples of components that produce sequences of
 >> documents where (a) the order of the documents within that sequence
 >> matters and/or (b) the sequence can contain duplicate documents?
 >
 > Can you construct duplicate documents at all in the pipeline?  I
 > think we had agreed some time ago that the pipeline itself has
 > copying semantics: if a component modifies an input document
 > (assuming the implementation provides a way to do that) it doesn't
 > affect other components that have the same document as input.  It
 > would be consistent to say that no standard components generate
 > sequences with the same ("eq") document twice.  I suppose a
 > user-written component under a given implementation might be able to
 > generate a sequence with duplicate documents

A good question, which I asked as well in my previous reply: I don't
know what in means in XProc to have "the same document" several times
in a sequence. If we do not have this at all, then again we don't have
a problem with node-sets at all.

-Erik

-- 
Orbeon - XForms Everywhere:
http://www.orbeon.com/blog/

Received on Monday, 5 June 2006 17:40:17 UTC