Alternate "parameters" draft

We seem to have come to a kind of stalemate over parameters.

Several members of the WG oppose changing the status quo on the basis of
simplicity and perceived marginality of the use cases that we cannot
satisfy with the status quo.

Several members of the WG want to change the status quo in order to
address perceived weaknesses in, and to satisfy use cases that cannot be
satisfied with, the status quo.

We have a deadline. We can't let this drag out indefinitely.

Most proposals to change the status quo have received little in the way
of support, but Jeni's most recent suggestion that we provide parameters
through an input seems to have garnered support from at least Alessandro
and I (and presumably Jeni :-).

In an effort to see how much violence this would do to the
specification, I've attempted to implement it:

  http://www.w3.org/XML/XProc/docs/alternate/

(with diffs, follow the "Revision markup" link)

Some observations:

1. To my eye at least, it does relatively little violence to the spec.

2. If you add nothing to your pipelines, if you make no changes to them
   at all, the semantics of parameters are exactly the same as the status
   quo.

3. If you need more control over parameters, you now have tools to
   accomplish that control.

4. It relies on implicit, default declarations for some port names but
   that doesn't feel much different than our current story about default
   inputs and outputs.

5. There's room for argument about the names of things, of course. I
   implemented "parameter input ports" with a parameters=yes attribute on
   p:input as Jeni suggested. If we adopt this proposal in spirit, I
   think we could reasonably decided to introduce a p:parameter-input
   element instead.

In the interest of full disclosure, points 2 and 4 interact a little
bit. If you happen to have a pipeline with a port named "parameters"
then you won't get exactly the current status quo behavior, but (1)
that's unlikely today and (2) you can easily work around it.

Comments?

                                        Be seeing you,
                                          norm

-- 
Norman Walsh <ndw@nwalsh.com> | The human race consists of the
http://nwalsh.com/            | dangerously insane and such as are
                              | not.--Mark Twain