Marty, I was suggesting first that we might not need messageOrderSemantics and we could do away with this attribute. I was suggesting second, that it is not particularly useful to tie MessageOrder to ConversationId. I did not mean to imply that MessageOrder would be outside the confines of a Conversation. We have no means of ending a Conversation and I suspect it will be common for Conversations to never end (why should they?). We do not specify that a ConversationId must be kept in storage anywhere in the spec. I am looking for another way -- say a new set of ordered messages could include the start number so the Receiving MSH does not have to keep messages past persistDuration? I don't know the solution but I think MessageOrder is broken. IMO, keeping information in persistent store forever is not the right answer, but I will go with that if it will get us past this problem. David.