RE: [sca-bindings] ISSUE-22: Callbacks for binding.ws

One difference is that I’m assuming that we want to avoid introducing new SOAP headers into the WS-* world (let me know if you disagree). The approach that we’ve adopted for JMS includes the introduction of a new “scaCallbackQueue” header (which is called a user property in JMS). If we want to avoid creating a new SOAP header, then I think we need to figure out how to use headers that have already been defined in some WS-* standard and use it in a way that is in keeping with the standard.

Michael

From: Eric Johnson [mailto:eric@tibco.com]
Sent: Friday, February 22, 2008 4:50 PM
To: Michael Rowley
Cc: OASIS Bindings; Anish Karmarkar; Jim Marino
Subject: Re: [sca-bindings] ISSUE-22: Callbacks for binding.ws

Am I missing something here?

Suppose for a moment that you ignore that "anonymous" reply channel in HTTP, and every message uses WS-Addressing for a response (although potentially it uses the "anonymous" channel).

How is this problem of callbacks over WS binding different from the four (five? six?) week effort on JMS that we (but mostly Simon H.) went through trying to figure out how to handle the JMSReplyTo header, depending on MEP, and callbacks? With JMS there is a clear upside to using the JMSReplyTo header, in that it is already a "Destination", thus overcoming some potential limitations.

If this is the same problem, does it deserve a solution that follows the same pattern? Or, is it a characteristically different problem (as I think it is), in that there isn't any "blessed" "reply" header that is any more special than any other.

-Eric.

Michael Rowley wrote:

I’d like to get this topic started. I’ve narrowed the subject line from the original Issue 22 title, since I’d like this particular thread to be on how callbacks could be handled in the WS-* world. We can handle conversations and other bindings on other threads.

First, I’ll assume that we will try to use WS-Addressing, if possible.

My first thought is that it would be preferable to be able to leverage the ws-ReplyTo field, since I believe that it should be possible to distinguish replies from callbacks, and I also believe that callbacks should go to the same place that replies would go to. I have a vague recollection that Anish preferred the use of <wsa:from> rather than <wsa:replyTo> for passing callback ID information. Unfortunately, I can’t find an email to that effect, so I’ll ask that he confirm or deny that.

I've been thinking that the client that is going to receive callbacks might want the reference parameters that would be available if the service provider follows the rules from the "Formulating a Reply Message" section of the WS-addressing spec.

One way that a callback could be distinguished from a reply is that the callback could have a <relatesTo> header that uses a relationship type of "oasis.org/isCallbackFor" and a reference to the messageID that the callback is in response to. I haven’t seen other uses of the <relatesTo> header, but it seems like this is exactly the sort of thing it is meant for.

Michael

From: Eric Johnson [mailto:eric@tibco.com]
Sent: Monday, February 04, 2008 2:45 PM
To: Mike Edwards
Cc: OASIS Bindings
Subject: Re: [sca-bindings] ISSUE-22: The Bindings specifications should provide exemplary Implementations for a) Callbacks and b) Conversations

Logged as http://www.osoa.org/jira/browse/BINDINGS-22

-Eric.

Mike Edwards wrote:

Raiser: Mike Edwards

Target: Web Services Binding specification, JMS Binding Specification, JCA Binding Specification

Description:

At present, it is not clear which, if any, of the Bindings specifications enable the implementation of two important
features of SCA described in the Assembly specification - namely Callback interfaces and Conversational
interfaces.

Each of the Bindings specifications should explicitly declare if it is possible to support each of these features.

For each of the Bindings specifications that claim to support either or both of these features, the specification
should provide a full description of at least one exemplary implementation of the feature using the Binding
technology described in the specification. Multiple alternative implementations are permitted and may be
added to the specification.

For example, it may be possible to implement Callbacks using WS-Addressing capabilities with Web services.
If so, and example, showing the use of appropriate features of WS-Addressing and other relevant WS-*
capabilities should be added to the specification. If an alternative exists using (say) WS-Context, then an
example based on that technology can also be provided.

Proposal:

None at present.

Yours, Mike.

Strategist - Emerging Technologies, SCA & SDO.
Co Chair OASIS SCA Assembly TC.
IBM Hursley Park, Mail Point 146, Winchester, SO21 2JN, Great Britain.
Phone & FAX: +44-1962-818014 Mobile: +44-7802-467431
Email: mike_edwards@uk.ibm.com

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