[wsrp] [CR309] - Specify lax processing of extensions element

[Rich Thompson <richt2@us.ibm.com>]

Location: Types schema
Requested by: Subbu Allamaraju
Current Text:
   <complexType name="Extension">
     <sequence>
       <any namespace="##other"/>
     </sequence>
   </complexType>

Proposed Text:
   <complexType name="Extension">
     <sequence>
       <any namespace="##other"
processContents="lax"/>
     </sequence>
   </complexType>

Reasoning: The current definition of the
Extension type makes it hard for producers/consumers/intermediaries to
validate the Envelope of messages using extensions.

If a producer/consumer uses extensions but
does not make it available to the receiver/intermediary (very common in
practice), and if the 
receiver/intermediary is an off-the-shelf
tool without entity resolution support, it will conclude that the message
is invalid.

By adding processContents="lax",
we can instruct the receiver/intermediary to try to validate on a best-effort
basis.

An alternative is to specify "skip"
for processContents. But I'm not sure of any advantage of this choice.