ASSEMBLY 132: Microsoft technical comment about the SCA Assembly Modelspecification #1 - Proposal

[Mike Edwards <mike_edwards@uk.ibm.com>]

Folks,

What follows in this email is a proposed
response to the Microsoft technical comment on the SCA Assembly Model specification.
I believe that it reflects some of the
initial discussions that we have had on this topic.

Comments welcome.


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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.
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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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