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Sequence Number Protocol

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Action: create Harmonization: add priorTransmission to support Transmission Sequencing proposal to add blue class.

The Sequence Number Protocol is an HL7-defined application protocol to guarantee in-sequence delivery of interactions.


  • (Grahame)I don't believe that there's any use case for the sequence number protocol now that we've done what we've done with the acknowledgement paradigm. I think that we should deprecate the concept.
    • (Rene) The underlying messaging infrastructure may provide reliable delivery, but it may not provide in-order delivery.
    • From: Test Cases (Lloyd) Suggest that the discussion of sequence number indicate that it only applies where either acceptAckCode is ‘AL’ (Always) or where acceptAckCode is ‘NE’, responseMode is ‘I’ (Immediate) and the outgoing interaction’s has receiver responsibilities that all have associated interactions. Rationale: The sequence # protocol depends on their being an immediate response to every outgoing message. These identified constraints are the only two mechanisms which ensure that such a combination will exist.
    • 2006-05-09: There is an apparent collision. If there is no immediate acknowledgment, and in-order delivery is essential, then the infrastructure layer must not only be reliable but also must ensure in-order delivery. After discussion, we came to no agreement about whether we should address this at the application layer or push the requirement down to the infrastructure.