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Subject: NEW ISSUE - Allignment and refinement of defintions for DA - Restatement
This email is a recast of my earlier email, which focuses more on the problem, taking out some of the proposed solution: in the earlier email I prefer this to be the new issue for discussion by the TC NEW ISSUE – Alignment and Refinement of Definitions for Delivery Assurances Description: I took an action Item to align the Delivery Assurance definition text in the body document with the resolution of Issue 009. Source: Tom Rutt, Fujitsu Justification: The resolution of Issue 009 is documented at: http://www.oasis-open.org/apps/org/workgroup/ws-rx/download.php/14682/ReliableMessagingIssues.xml#i009 : It is best if the Delivery assurances are defined in only one place in the document. There is a discrepancy with the current text in secton 2 and the resolution of issue 009, regarding the necessity for raising an error on at least one endpoint. The definition in the current text of DA in Section 2 : " There are four basic delivery assurances that endpoints can provide: - AtMostOnce Messages will be delivered at most once without duplication or an error will be raised on at least one endpoint. It is possible that some messages in a sequence may not be delivered. - AtLeastOnce Every message sent will be delivered or an error will be raised on at least one endpoint. Some messages may be delivered more than once. - ExactlyOnce Every message sent will be delivered without duplication or an error will be raised on at least one endpoint. This delivery assurance is the logical "and" of the two prior delivery assurances. - InOrder Messages will be delivered in the order that they were sent. This delivery assurance may be combined with any of the above delivery assurances. It requires that the sequence observed by the ultimate receiver be non-decreasing. It says nothing about duplications or omissions. " while the current text for resolution of issue 009 adds the following for DA policy assertion: " <wsrm:DeliveryAssertion mode="[AtLeastOnce|AtMostOnce|ExactlyOnce]" ordered="[xs:boolean]"? ...="" > /wsrm:DeliveryAssertion A policy assertion that makes a claim as to the delivery assurance policy observed by the destination endpoint. /wsrm:DeliveryAssertion/@mode This required attribute specifies whether or not all of the messages within an RM Sequence will be delivered by the RM Destination to the Application Destination, and whether or not duplicate messages will be delivered. A value of 'AtMostOnce' means that messages received by the RM Destination will be delivered to the Application Destination at most once, without duplication. It is possible that some messages in a sequence may not be delivered. A value of 'AtLeastOnce' means that every message received by the RM Destination will be delivered to the Application Destination. Some messages may be delivered more than once. A value of 'ExactlyOnce' means that every message received by the RM Destination will be delivered to the Application Destination without duplication. /wsrm:DeliveryAssertion/@ordered This attribute, of type xs:boolean, specifies whether, or not, the destination endpoint ensures that the messages within an RM Sequence will be delivered in order, by the RMD to the AD. Order is determined by the value of the RM message number. Ordered delivery would mean that the messages would be delivered in ascending order of the message number value. A value of 'true' indicates that messages will be delivered in order. A value of 'false' makes no claims as to the order of delivery of the messages within a RM Sequence. If omitted, the default implied value is 'false'. Proposals: The proposal to resolve this ISSUE is presented in Three Steps. Step 1) of Proposed Resoluton: Change the use of in line definitions in the proposal for Issue 009 to references to the definitions in section Resulting text for Proposal for Issue 009: “ <wsrm:DeliveryAssertion mode="[AtLeastOnce|AtMostOnce|ExactlyOnce]" ordered="[xs:boolean]"? ...="" > /wsrm:DeliveryAssertion A policy assertion that makes a claim as to the delivery assurance policy observed by the destination endpoint. /wsrm:DeliveryAssertion/@mode This required attribute specifies which delivery assurance is asserted. A value of 'AtMostOnce' means that the Delivery Assurance “at Most Once, defined in section xxx, is asserted. A value of 'AtLeastOnce' means that the Delivery Assurance “At Least Once”, defined in section xxx, is asserted.. A value of 'ExactlyOnce' means that the Delivery Assurance “Exactly Once”, defined in section xxx, is asserted. /wsrm:DeliveryAssertion/@ordered This attribute, of type xs:boolean, specifies whether, or not, the “in order” reliability function defined in section xxx is asserted. . A value of 'true' asserts that the “in order” reliability function is required. A value of 'false' asserts that the “in order” reliability function is not required. If omitted, the default implied value is 'false'. “ Step 2) of Proposed Resolution: Clarify Definitions of Delivery assurances, including the requirment for error indication. We need to align the two definitions and put the resulting agreed text in section 2: - the definitions of AtLeastOnce and of ExactlyOnce from Issue 009 do not mention the possibility of an error (delivery failure) while they do in the current core spec definition. Is that intentional, or a lapse? It seems the the same reasons that may lead an RMD to drop received messages under AtMostOnce, may also apply under AtLeastOnce (e.g. some resource shortage). The difference seems to be about proper error raising/notification when a received message is not delivered.. - Similarly, AtMostOnce as defined in the resolution to issue 009 assumes that duplicates are never delivered - that seems stronger than the original requirement in the core spec that says "... or else an error will be raised". These need to be aligned one way or the other. -- ---------------------------------------------------- Tom Rutt email: tom@coastin.com; trutt@us.fujitsu.com Tel: +1 732 801 5744 Fax: +1 732 774 5133
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