[Xml-compile] explain(): required and optional params

[Joshua Keroes]

My project leverages explain() to help self-document every WSDL action
that we use. That's saved me lots of work and I absolutely love it.

The project handles many of parameters by itself; rearranging them
here, providing defaults there, and overriding values elsewhere.

Instead of giving the user the WSDL action's parameters which aren't
relevant any more, I'd like two structures: the WSDL's required params
and the optional params.

Short of evaluating the explain() output and parsing the comments, I'd
love a recommendation on a less fragile way to get at those
parameters.

Thanks,
Joshua