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Subject: Re: [sca-bindings-comment] Response to: "Microsoft technical comment:Develop interoperable approach notspecific to SCA for callbacks"

Here are my immediate thoughts, in response, for the TC's consumption:

Michael Champion wrote:

Thank you for considering Microsoft's suggestion for improving the SCA Web Services Binding spec's interoperability (http://www.osoa.org/jira/browse/BINDINGS-87).


We suggested that Web Services callbacks in the SCA Web Services Binging spec should interoperate with comparable frameworks such as JAX-WS and WCF, and not be limited to various implementations of SCA.  This would promote the original goals of the Web Services standards to achieve wire-level interoperability among diverse run-times and platforms.

I'm unaware of anything in JAX-WS that addresses callbacks, so I don't understand that point, or how it is comparable.  Nor am I aware of anything that we've specified that prevents a vendor from using JAX-WS to implement callbacks support within the SCA environment.  Presumably implementation experience will reveal details here?

With respect to WCF, I'm not aware of its capabilities, and whether or not it provides anything equivalent to the callback functionality of SCA.  Does anyone else on the TC have insight into this?

At the wire level, what we've describe remains interoperable and compatible.  Seems to me like the actual issue is at the protocol level.


The SCA Binding TC responded by saying that the SCA Web Services binding protocol "defines an *SCA* Web service callback protocol standard” and that it "is not meant to satisfy general purpose callback requirements with a broadest scope possible". In other works, the TC believes that the SCA Web Services callbacks will NOT be interoperable with non-SCA implementations

That sounds incorrect to me.  Seems like it is completely out of scope for an SCA TC to dictate how or if any standard outside of SCA reaches compatibility with something inside of SCA.  Nothing prevents other implementations (Mike Champion's word choice) from achieving interoperability.


The TC's response goes on to say that "This TC does believe that it should define an interoperable Web services protocol that implements SCA callback and it has done that. It does not believe that it is in the scope or interest of this TC to define a callback protocol for all architectures and programming models." We respectfully find this statement contradictory, unless the TC defines the term "interoperability" in its narrowest form: SCA implementations will only be interoperable amongst themselves, and not with other frameworks and runtimes. We would find this unfortunate, as OASIS is committed to broad interoperability, especially when it comes to use of Web Service wire protocols.  It would be better to standardize a Web Services callback in a separate spec, with the participation of all vendors who build platforms and products that support Web Services wire protocols.

Yes, we define interoperability amongst SCA runtimes (including from different vendors), since that's within the scope of our charter.  The "narrowest" sense would be only interoperability among a single vendor (see JMS itself, the "binding.sca" binding, and various Microsoft networking protocols, at some point in time.).  So I disagree with the characterization of this as the "narrowest" possible form of interoperability.  Further, we don't deny the utility of a broad specification, and yes, we believe interoperability at a larger scale would be useful.  It just isn't in our charter.

Is Microsoft explicitly requesting a change in charter?  If so, they should explicitly state that.


It is clear from  [1] that the TC is aware that interoperability with non-SCA runtimes is an issue. The TC discussed the idea of moving the callback portion of the protocol into its own document in order to address "the use case of non-SCA clients does walk into the more general territory alluded to by MS." We highly recommend that the Binding and Assembly TCs work together to design a Web Services Binding spec that is interoperable with non-SCA technologies.  Without interoperability, software developers and users will find it difficult to use SCA in the heterogeneous, multi-vendor environments that all our customers live in.

Absolutely nothing here prevents vendors from building compatible systems with both SCA and non-SCA parts that interact.  In fact, we expect it.  Further, when bridging from a non-SCA environment to an SCA environment, a vendor such as Microsoft should only have to implement compatibility with the SCA WS Callbacks mechanism once, and it should work with all vendors providing SCA environments.  If they believe this last point is incorrect, it would be enormously useful for Microsoft to identify the specific oversights of the currently specified approach.



[1] http://www.oasis-open.org/committees/download.php/34064/SCA%20Bindings%20minutes%202009-09-03.doc



Michael Champion


From: Simon Holdsworth [mailto:simon_holdsworth@uk.ibm.com]
Sent: Thursday, September 17, 2009 7:04 AM
To: sca-bindings-comment@lists.oasis-open.org
Subject: [sca-bindings-comment] Response to: "Microsoft technical comment: Develop interoperable approach notspecific to SCA for callbacks"


This is a formal response of the OASIS SCA Bindings technical committee to the "Microsoft technical comment: Develop interoperable approach not specific to SCA for callbacks" which was sent to the SCA Bindings public comments list.

This is the agreed response of the technical committee as a whole and was approved unanimously at the meeting
of the TC which took place on September 3rd 2009.


Thanks for taking the time to review the specification, sending your public review comment [1], and for sharing you thoughts. They are much appreciated.

The public review comment at [1] suggests that: "... the work of defining a Web Service callback standard is best done by the appropriate Web Services working groups in OASIS in the broadest scope possible. This will foster a general interoperable mechanism for all architectures and programming models that use standard Web Services protocols on the wire."

There is a misunderstanding on the commenter's part that the SCA Web Services Binding defines a (generally applicable) "Web Service callback standard." The binding defines an *SCA* Web service callback protocol standard that provides the wire-level details for implementing an SCA callback defined by the SCA Assembly specification [2]. [2] defines a callback mechanism that satisfies the needs of the SCA Assembly model and is not meant to satisfy general purpose callback requirements with a broadest scope possible. Furthermore, there does not exist any other OASIS Web Services Working Group or a Technical Committee that specializes in Web Services that has callbacks in its charter scope. This TC *does* specialize in Web services and is chartered to produce a Web services binding for SCA.

This TC does believe that it should define an interoperable Web services protocol that implements SCA callback and it has done that. It does not believe that it is in the scope or interest of this TC to define a callback protocol for all architectures and programming models.

WRT your comment about SCA Assembly specification Section 7.4, we respectfully request you to share that feedback with the SCA Assembly TC [3], as the SCA Assembly specification is not owned by and is not in scope for this TC.

[1] http://lists.oasis-open.org/archives/sca-bindings-comment/200908/msg00000.html
[2] http://docs.oasis-open.org/opencsa/sca-assembly/sca-assembly-1.1-spec-cd03.pdf
[3] http://www.oasis-open.org/committees/tc_home.php?wg_abbrev=sca-assembly


Follow-up comments are welcome.

Regards, Simon

Simon Holdsworth
STSM, SCA Bindings Architect; Master Inventor; OASIS SCA Bindings TC Chair
MP 211, IBM UK Labs, Hursley Park, Winchester SO21 2JN, UK
Tel +44-1962-815059 (Internal 245059) Fax +44-1962-816898
Internet - Simon_Holdsworth@uk.ibm.com


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