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Subject: RE: [ebxml-msg] Sequences and sequence sharing
Pim: inline -----Original Message----- From: Pim van der Eijk [mailto:pvde@sonnenglanz.net] Sent: Tuesday, September 02, 2008 1:08 PM To: ebxml-msg@lists.oasis-open.org Subject: [ebxml-msg] Sequences and sequence sharing Hello, To follow up on the discussion on (re-)using sequences from two weeks ago: which ebMS messages are sent on the same WSRM sequence? This is more about ebMS 3.0 in general than about multihop. Jacques mentioned a default assumption that each Pmode is associated with a distinct sequence. <JD> I should have been more nuanced: Core V3 says (B.2.1): "It is RECOMMENDED that all messages transmitted over a same sequence use the same MPC. This becomes a requirement for the In-Order reliability contract." So messages from an RM sequence should not go over several MPCs, but the reverse is not a problem: several RM sequences can use the same MPC. The constraint is more about RM sequence vs. MPC, rather than Pmode. Now, each leg of an MEP in a Pmode is assigned to only one MPC so far (I ignore here the case of "sub-channels" of an MPC). But an MPC can easily be shared by several Pmodes. The key point about RM sequences, is that (B.2.1) we require that the same Delivery Assurance(Ordering, At-Least-Once....) be used for all messages of the same sequence. Given this, a Pmode could share a sequence (and an MPC) with other Pmodes, and also a Pmode (which is usually associated with a single Deliv Assurance, at least for each one of its "legs") can still make use of several RM sequences for a single "leg" - e.g. a pool of sequences - provided they are associated with same delivery assurance.</JD> 1) In the document on routing examples (http://www.oasis-open.org/apps/org/workgroup/ebxml-msg/document.php?doc umen t_id=28981) I discuss a number of routing scenarios. The simplest case assumes routing is based on To:PartyId only. It basically asserts for an I-Cloud that any ebMS message, including messages to be sent reliably, is handled by the same final MSH. This means that an ebMS MSH can optimize its sequence creation, as some Pmodes can use the same sequence. It was suggested to leave this out of the multihop specification and leave this to implementers as it is an optimization rather than a potential conformance or interoperability issue. 2) Section 2.5 mentions a situation where a message is routed differently based on a message property value. This means that there have to be different sequences based only on property values. Can there be two Pmodes that are the same except for a particular message property value? <JD> I think so. If not, the routing document should not refer to routing based on properties. 3) The ebMS 2.0 message ordering module associates ordering with ConversationId. Do we want to support a similar model with ebMS 3.0? If we have a business process where "conversations" consist of a "PlaceOrder" action, followed by one or more "ChangeOrder" actions followed by an option "CancelOrder" action and they are to be processed in order, then the MSH must use the same sequence to send them. How and where is this specified? <JD> I think we have in the Pmode some way to associate a conversation with a delivery assurance. See Pmode.Reliability.Correlation and the like. Pim --------------------------------------------------------------------- To unsubscribe from this mail list, you must leave the OASIS TC that generates this mail. Follow this link to all your TCs in OASIS at: https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php
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