Arvola, If AckRequested is *true* in the CPA, then does the AckRequested element have to appear? If it MUST appear, then why have it in the CPA? I think the Receiving MSH must send an Acknowledgment in this case even if AckRequested does not appear. Actually, I would prefer that AckRequested MUST NOT appear if the CPA says *true* or *false*. If AckRequested is *perMessage* in the CPA, then what happens if the AckRequested element does not appear? The spec says this means no Acknowledgment. The default then is *false* if the CPA says *perMessage*. I think we should not have multiple rules about *perMessage*. If a default is provided in one case, then it should work the same in all cases. Since the absence of an Acknowledgment element means *false* then the absence of duplicateElimination should also mean *false* and the absence of a signed attribute should mean *false* (or in all cases it means take the default). David.