Source without a step

Irrespective of the syntax, it will be possible to specify a source
without a port, e.g.,

  <p:input port="document" source="!result"/>

What does this mean?

Option 1: It's an error and we come back to it later when we're
talking about abbreviations.

Option 2: the "result" port of the preceding step. It's an error if
there's no preceding step.

Option 3: the "result" port of the preceding step or the parent step
if there's no preceding step. It's an error if there's no preceding
or parent step.

Option 4: The "result" port of the nearest "upstream" step that has
an output port named "result". It's an error if no such step exists.

Or something else?

                                        Be seeing you,
                                          norm

-- 
Norman Walsh
XML Standards Architect
Sun Microsystems, Inc.