Integrating XProc into XPath

Hello world,

In some senses, the biggest gains in XProc usability would come from
the ability to use XProc more naturally in XPath expressions. One could
even imagine, if we made that possible, that XProc could be used from
other XPath frameworks.

Two crazy ideas drifted through my head this morning:

  <p:variable name="whatever" as="map(xs:string,item()*)">
     { subpipeline }
  </p:variable>

That is, the value of that variable is a map from the names of the
output ports on the final step to the sequences of items that appeared
on the respective port.

There'd have to be some pretty tight constraints about what a
variable's pipeline can "see" or you'd be able to write loops.

That extends pretty naturally to

  <p:function name="myfunc" as="map(xs:string,item()*)">
    <p:param name="input" as="document-node()*"/>

    <p:identity>
      <p:input port="source" select="$input"/>
    </p:identity>
  </p:function>

Here a restriction that says no pipes that "leave" the function are
allowed bites less severely because you can pass anything you need
into it. It's also self-contained so it can't introduce loops.

Presumably you could later do:

  <p:store href="{if (empty(map:get($whatever,"result"))
                      or empty(map:get(myfunc(($a,$b,$c)),"result")))
                  then $this
                  else $that}"/>

It would probably be convenient to think of a way to make it possible
for $whatever and myfunc() to return a single sequence and not a map
in the case where there was only one output port.

                                        Be seeing you,
                                          norm

-- 
Norman Walsh
Lead Engineer
MarkLogic Corporation
Phone: +1 512 761 6676
www.marklogic.com