I think you and Tim should converge on a single clean alternative to WSDL, with a better name. NSDL is too personal, and SMEX-D sounds like something you scrape out from under your fingernails.

I think the SMEX-D framework is the better one overall, but since it provides nothing for compiler binding/RPC, it needs to be enhanced with elements from NSDL. On the response side, the NSDL elements result and fault Do The Right Thing, and should be allowed within smex-d:response.

On the request side, provide something like a prototype element, a child of smexd:request, which shows you what the document to be sent looks like, and a list of nsdl:parameter elements, likewise children of smexd:request, whose values are plugged into the prototype.

An obvious tactic for plugging in would be: If an element or attribute name in a nsdl:parameter matches an element or attribute name inside the prototype, replace it. If $name is found in character content or an attribute value within the prototype, replace it too.

Wuddaya think? RELAX and TREX merged and are doing Great Things.