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Subject: Re: [sca-bindings] [NEW ISSUE]: Clarify optionality of SHOULD statementBJM60001


Logged as: http://www.osoa.org/jira/browse/BINDINGS-159

Note that I took the liberty of changing the title of the issue to reflect the normative statement under consideration: BJM60001.

-Eric.

On 4/11/11 8:37 AM, Simon Holdsworth wrote:
OFD0F48E78.BCCAE60D-ON8025786F.0053E71E-8025786F.0055CC5D@uk.ibm.com" type="cite">Target:  sca-jmsbinding-1.1-csd05.pdf

Description:

The JMS binding specification includes statement BJM60001 with a SHOULD keyword:

For an SCA reference with a JMS binding and unidirectional interface, when a request message is sent as part of a one-way MEP, the SCA runtime SHOULD NOT set the JMSReplyTo destination header in the JMS message that it creates, regardless of whether the JMS binding has a response element with a destination defined [BJM60001]

We need to clarify whether this is an optional part of the JMS binding spec.

Proposal:

SHOULD was deliberately selected for this statement when the JMS message exchange patterns was reviewed and approved.  The concern expressed at the time was that for some reason of interoperation with an existing JMS application a one-way interaction may need to include a JMSReplyTo destination.  Although the interaction is modelled as a one-way operation with no callback in SCA, a JMS application might still expect the JMSReplyTo destination to be set to identify a 3rd-party to which an additional message is to be sent.  For that reason we did not want to preclude the JMSReplyTo from being set by the SCA runtime through other configuration/runtime action by making this statement a MUST.  However we wanted to promote the practice of a null JMSReplyTo for one-way operations.  The only way we could allow the flexibility without a SHOULD is to make this statement non-normative by replacing it with something like the following text:

The JMS specification provides the JMSReplyTo header as the way for a JMS application to identify the destination on which replies or other messages are to be placed that relate to the one being sent.  For one-way requests sent by SCA references with unidirectional interfaces, the JMSReplyTo will not usually be set as no reply or other related message is expected.

My expectation is that setting a non-null JMSReplyTo for a one-way request with no callback to identify a third party is not a common pattern, and not one we would want to encourage in an SOA framework, so I would not object to a resolution which replaces the SHOULD by a MUST, but I wanted to air the original discussion so we don't jump to this conclusion.

---------------------------------

Simon Holdsworth





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