A schema for each mep?

At last f2f we discussed about rules to retrieve default values for 
message-related constructs.
It seems interesting to have a mep schema for at least two reasons:
    - allow the validation of the content of each wsdl:operation instance
    - allow defaulting of values (such as messageRef or direction)
The idea would be that any author of a wsdl mep spec would also write a 
mep schema.

Attached are examples of what could resemble such schemas (these are not 
complete schemas, for instance the open content model is not taken into 
account). There are two examples, one to accomodate the current notation 
for contents in the wsdl:operation construct and one to accomodate the 
notation as proposed by Jean-Jacques. In each file (example1.xml and 
example2.xml), a <syntax> element is related with a <schema> element. 
Each schema should do some validation of the <syntax> example and give 
default values when possible.

What do you think ? Is this worth continuing exploring this subject?
    Youenn

Quick question: in the case of meps with more than one input message, we 
might have several <wsdl:input> in a <wsdl:operation> construct. Is it 
possible with XML Schema to give a different type for each of these 
<wsdl:input>? If I recall correctly I would say no, but I am not very 
sure (If it is not possible, it might lead to problems for defining 
mep's schemas, with XML Schema at least).