[Issue 2] Version 2: How to implement SCA callbacks using SOAP --a proposal

[Anish Karmarkar <Anish.Karmarkar@oracle.com>]

I took an action at the f2f to update the proposal that I had sent out [1] based on the feedback received during the f2f and the mailing list.
Based on the feedback, I have made two changes: a) changed the case of 'must' and b) instead of saying "... callback EPR obtained from *the* request message ...", it now says "... callback EPR obtained from *a* request message ..."

V2 does not the incorporate the comments/feedback for which there wasn't an agreement.

-Anish
--

[1] http://lists.oasis-open.org/archives/sca-bindings/200807/msg00027.html

Proposal v2:
1) Every request message that invokes the forward interface MAY contain the wsa:From SOAP header block. The wsa:From header block, if present, specifies the Callback EPR. If wsa:From header block is not present, then the wsa:ReplyTo, if present, specifies the Callback EPR. If neither wsa:From nor wsa:ReplyTo are present in the request message of the forward interface, the service MUST generate a SOAP Fault.

2) Every request message that invokes the forward interface MUST contain the wsa:MessageID SOAP header block. If a request message that invokes the forward interface does not contain the wsa:MessageID then the service must MUST generate a SOAP Fault.

3) When the service wants to invoke the callback interface, it utilizes the Callback EPR obtained from the a request message, as specified in step 1, that invoked the forward interface. Once the Callback EPR is selected, the service MUST follow the rules defined in WS-Addressing 1.0  section 3.3 to invoke operations on the callback interface. In addition, when the service invokes the callback interface, it MUST include a wsa:RelatesTo SOAP header block. The wsa:RelatesTo SOAP header block MUST have the relationship type value of "http://docs.oasis-open.org/opencsa/sca-bindings/callback" and the related message id is the wsa:MessageID of the message from which the Callback EPR was obtained.

Scenarios:
S: service with a bidirectional interface
R: reference connected to service S

The wire binding (in both directions) uses SOAP.

The forward interface consists of only one one-way operation: YouRIt()
The callback interface consists of only one one-way operation: NoYouRIt()

R invokes YouRIt(). Let's call this invocation R1 and it sets the callback address to RC1. S then calls NoYouRIt() twice: S1 and S2
R invokes YouRIt() again. Let's call this invocation R2 and it sets the callback address to RC1. S then calls NoYouRIt() once: S3
R invokes YouRIt(). Let's call this invocation R3 and it sets the callback address to RC2. S then calls NoYouRIt() twice: S4 and S5.

Wire messages:
R1:

<soap:Envelope ...>
 <soap:Header>
   <wsa:From>
     <wsa:Address>http://example.com/callback</wsa:Address>
     <wsa:ReferenceProperties>
       <myNS:SomeID>1</myNS:SomeID>
     </wsa:ReferenceProperties>
   </wsa:From>
   <wsa:MessageID>urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6</wsa:messageID>
    ...
 </soap:Header>
 <soap:Body>
   ...
 </soap:Body>
</soap:Envelope>

S1, S2:

<soap:Envelope ...>
 <soap:Header>
   <wsa:To>http://example.com/callback</wsa:To>
   <myNS:SomeID>1</myNS:SomeID>
   <wsa:RelatesTo RelationshipType="http://docs.oasis-open.org/opencsa/sca-bindings/callback">
   urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6
   </wsa:RelatesTo>
    ...
 </soap:Header>
 <soap:Body>
   ...
 </soap:Body>
</soap:Envelope>

R2:

<soap:Envelope ...>
 <soap:Header>
   <wsa:From>
     <wsa:Address>http://example.com/callback</wsa:Address>
     <wsa:ReferenceProperties>
       <myNS:SomeID>1</myNS:SomeID>
     </wsa:ReferenceProperties>
   </wsa:From>
   <wsa:MessageID>urn:uuid:f81d4fae-8dec-11d0-a765-00a0c91e6bf6</wsa:messageID>
    ...
 </soap:Header>
 <soap:Body>
   ...
 </soap:Body>
</soap:Envelope>

S3:

<soap:Envelope ...>
 <soap:Header>
   <wsa:To>http://example.com/callback</wsa:To>
   <myNS:SomeID>1</myNS:SomeID>
   <wsa:RelatesTo RelationshipType="http://docs.oasis-open.org/opencsa/sca-bindings/callback">
   urn:uuid:f81d4fae-8dec-11d0-a765-00a0c91e6bf6
   </wsa:RelatesTo>
    ...
 </soap:Header>
 <soap:Body>
   ...
 </soap:Body>
</soap:Envelope>

R3:

<soap:Envelope ...>
 <soap:Header>
   <wsa:From>
     <wsa:Address>http://example.com/callback-other</wsa:Address>
     <wsa:ReferenceProperties>
       <myNS:SomeID>2</myNS:SomeID>
     </wsa:ReferenceProperties>
   </wsa:From>
   <wsa:MessageID>urn:uuid:f81d4fae-9dec-11d0-a765-00a0c91e6bf6</wsa:messageID>
    ...
 </soap:Header>
 <soap:Body>
   ...
 </soap:Body>
</soap:Envelope>

S4, S5:

<soap:Envelope ...>
 <soap:Header>
   <wsa:To>http://example.com/callback-other</wsa:To>
   <myNS:SomeID>2</myNS:SomeID>
   <wsa:RelatesTo RelationshipType="http://docs.oasis-open.org/opencsa/sca-bindings/callback">
   urn:uuid:f81d4fae-9dec-11d0-a765-00a0c91e6bf6
   </wsa:RelatesTo>
    ...
 </soap:Header>
 <soap:Body>
   ...
 </soap:Body>
</soap:Envelope>