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Subject: Response to: "Microsoft technical comment about the SCA Assembly Modelspecification"

This is a formal response of the OASIS SCA Assembly technical committee to the "Microsoft technical comment about the
SCA Assembly Model specification" which was sent to the SCA Assembly 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 May 19th 2009.


The SCA Assembly technical committee thanks Microsoft for its comment on the SCA Assembly Model specification.

The Assembly TC is pleased to hear that Microsoft would like to see the SCA Assembly Model specification be as inclusive and as platform neutral as possible and that the SCA specifications should be open to a diversity of implementation choices.  This is a sentiment shared by the OASIS Open CSA Member Section as a whole and is one of the reasons why the charter of the Open CSA Member Section includes specific statements to this effect.

We note that Microsoft has a concern with a conformance requirement in section 13.2 which requires that an SCA Assembly conforming runtime implementation supports at least one of the implementation types for which a specification has been adopted by the Open CSA Member Section.

At first glance, this requirement might be regarded as a restriction on an SCA runtime implementation.  However, this is not our intention, as we shall explain.

First, as Microsoft rightly acknowledges, the SCA model is inherently extensible both in terms of the implementation types that may be used to build components and also in terms of the communication methods that may be used to connect service components.  The SCA model itself makes no restriction on the implementation language used for service components; neither does it make any restriction on the implementation technology chosen for the SCA runtime itself.  Indeed, there are some existing implementations of SCA which have already provided support for implementation types which go beyond the set which are currently described in the TC's affiliated with the Open CSA Member Section. We note that section 13.2 in no way restricts the support of new implementation types by an SCA runtime.

The reason for the requirement to support at least ONE of the implementation types adopted by the Open CSA Member Section has to do with the portability assurance that formal standardization and formal conformance gives to end-users.  If there were no requirement to support one of the implementation types covered by the Open CSA Member Section, this would mean that end users could have no assurance that the SCA runtime concerned really provides the functions laid down by the SCA specifications.  We believe that any new implementation type worthy of common usage should be brought into the standards fold, to give end-users assurance that it will work as expected, particularly where multiple runtimes support that implementation type.

The Assembly TC encourages Microsoft, and any other parties wanting to see SCA support for a wider range of implementation types, to bring forward specifications for those implementation types to OASIS, where they can be adopted by the Open CSA Member Section and developed as standards and subsequently added to the group of implementation types which qualify under section 13.2 of the SCA Assembly Model specification.  This might be done for an implementation language such as C# or PHP, for example.  We strongly believe that this approach will benefit the users of SCA, since it will give them an enhanced assurance of portability in a standards-based approach to building service components using those implementation types and also encourage multiple vendors to build conforming SCA runtimes and tools that support those implementation types.


Follow-up comments are welcome.

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

Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number 741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU

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