Detecting errors

Consider the following pipeline:

<p:declare-step name="main" ...>
  <p:input port="source"/>
  <p:output port="source"/>

  <p:declare-step type="px:unused">
    <p:input port="source"/>
    <p:output port="source"/>
    <px:undeclared/>
  </p:declarestep>

  <p:identity/>
</p:declare-step>

(a) Does this pipeline contain an error?
(b) Are implementations allowed to report it?
(c) Are implementations required to report it?

I think the answer to (a) is yes. I think the answers to (b) and (c)
should either both be yes or both be no, for interoperability reasons.
I'm inclined towards yes, but I'm not sure the spec gives a definitive
answer.

                                        Be seeing you,
                                          norm

-- 
Norman Walsh <ndw@nwalsh.com> | I'm NOT in denial!
http://nwalsh.com/            |