Issue - 227 - The messageExchange attribute doesn't handle parallel forEach

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Issue - 227 - The messageExchange attribute doesn't handle parallel forEach

Status: received
Date added: 24 Aug 2005
Categories: Syntax & semantics
Date submitted: 22 August 2005
Submitter: Chris Keller
Description: The messageExchange attribute doesn't handle parallel forEach.  Take the following example.  The BPEL programmer is dispatching multiple requests to a system and receiving messages from that system which require a reply.  The requests are correlated and independent so the programmer wishes to use the parallel forEach activity.

<process ...>
   ...
   <partnerLinks>
      <partnerLink name="workSystem" partnerRole="workHandler" myRole="workRequester"/>
      ...
   </partnerLinks>
   ...
   <forEach parallel="yes">
      <startCounterValue>...</startCounterValue>
      <finalCounterValue/>...</finalCounterValue>
      <scope>
        <correlationSets>
           <correlationSet name="CS" properties="..."/>
        </correlationSets>
        <sequence>
          <assign>...</assign>
          <invoke partnerLink="workSystem" operation="createWork"...>
             <correlations>
                <correlation initiate="yes" pattern="out" set="CS"/>
             </correlations>
          </invoke>
          <receive partnerLink="workSystem" operation="workResult"...>
             <correlations>
                <correlation initiate="no" set="CS"/>
             </correlations>
          </receive>
          <assign>...</assign>
          <reply partnerLink="workSystem" operation="workResult".../>
       </sequence>
   </forEach>
   ...
</process>

According to the current specification the moment the second receive is scheduled the process must throw a "conflictingRequest" fault as it is a request-response MEP and has the same partnerLink, operation and messageExchange as the first receive. However there is no way to create a messageExchange which would avoid it conflicting. The issue can be solved by introducing a locally defined partnerLink, but the messageExchange attribute was introduced so users would not need to do that when the partner is truly the same entity (in this case the workSystem partnerLink is the same entity for all iterations).

I suggest we revisit the proposal for a messageExchange to be scoped to allow users to create non-conflicting receives in this parallel forEach use case.
Changes: 24 Aug 2005 - new issue

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