[ISSUE 132] Rebuttal: Against the use of portability and functions asreasons for requiring one of the existing 4 languages

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

Jim,

Thanks for your comments.

First, I would like to point out that
we have built the Assembly testcase suite along the lines that you
want to see.  It is built in a
way that is language independent with all top level materials being
wholly composite based, and then with
replaceable language-specific implementations at the
bottom.

Availability of the testcase suite in
each of the OASIS supported language types is not a "convenience"
- it is a requirement.  We already
have Java, and C, C++ and BPEL are well advanced.  Others will be
added as their specifications come forward
to public review.

The second point about the testcase
suite is that it is not just a matter for the SCA runtime implementers.
The idea is that the conformance testcase
suite is available to all - anyone can take it and use it to 
verify that some SCA runtime conforms
to the specifications.  It is the open nature of the test suite that
is the biggest guarantee that SCA runtime
vendors will take it seriously - no one can bend their way
around it without facing the possibility
that users will catch them out.


The second question to address is what
you really think it means to "conform" to the SCA specifications.

One important thing is that SCA is extensible
and can accommodate the use of pretty well any implementation
technology and implementation language.
 Any vendor can do this at any time.  So SCA is very much open,
as you desire.

However, claiming conformance is something
else.  What does "claiming conformance" really mean?
To me, it means that the SCA runtime
meets the requirements of the relevant SCA specifications.  
I am sure there is real value to end
users in a claim of conformance - the end users can have  expectations
of a conforming system that it will
work in a certain way - and that the end users knowledge of SCA will apply
to the conforming system.  It is
clear that vendors also attach importance to claiming conformance too.

If conformance is to have any real meaning,
I believe that this must mean adhering to the letter of the spec.
Our current approach to this is to require
the passing of the test suite - as a minimum check.  There will always
be things that the test suite does not
check - and for those, the wording of the conformance points in the spec
is the tool that people can use.

So, let us say that we want a more "open"
approach to claiming conformance for a runtime that supports 
one or more implementation languages
not specified by any of the OASIS TCs.  How might we do this while
still retaining some meaning to the
term "conformance"?  Some thoughts:

- Might we allow a claim of conformance
for language "X" as long as there is a Test Suite for Assembly
that
uses implementation language "X"?

- Might we allow a claim for conformance
for language "X" as long as there is a specification for SCA
component
implementations written in lnaguage
"X"?  Without such a specification and in particular without
a definition of
how the componentType is calculated
for an implementation artifact written in language "X", how would
it be
possible to know that the test suite
was a valid test suite?

- Should it be required that the test
suite and the specification for language "X" is available publicly
with some
form of open terms?  I note that
the current OASIS TC specs and test suite are available to anyone on open
terms - so that anyone can take them
and run them.


What are your thoughts on this?

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

From:	Jim Marino <jim.marino@gmail.com>
To:	sca-assembly-comment@lists.oasis-open.org
Cc:	OASIS Assembly <sca-assembly@lists.oasis-open.org>
Date:	10/06/2009 02:07
Subject:	[sca-assembly] Rebuttal: Against the use of portability and functions as reasonsfor requiring one of the existing 4 languages

---

Hi,

I haven't had much time lately to participate in TC discussions on  
language conformance due to other commitments. However, I did have the
 
opportunity to discuss the technical merits of this issue at length  
with people from Microsoft. I think I understand where they are coming
 
from and believe there may be a way to accommodate Microsoft's  
concerns while also improving the SCA specifications.

Coupling conformance to the Assembly specification with one of the  
"official" TC languages places an unneeded and expensive burden
on  
potential implementors that may not support one of those languages.  
This is particularly evident given the OASIS requirement for two  
independent conformant implementations. The original spirit of  
assembly was language independence and that can be maintained. It  
seems the main sticking point is with conformance testing: namely, how
 
can language independent tests be created that verify assembly  
assertions?

As a proposal, I believe it is feasible to use composite  
implementations to create language independent verification tests. The
 
tests would make extensive use of the implementation.composite type as
 
well as service and reference promotions. The actual implementations  
would be contained in a separate contribution (or contributions) and  
made available to the using composite via the contribution import/ 
export mechanism. The verification tests would be run against the  
components using the composites and their promoted services, which  
would result in language independent conformance checks.

As a convenience, composites which used "official" language types
such  
as implementation.java or implementation.bpel could be made available.
 
However, it would also be possible for a vendor to supply their own  
composites that used a proprietary language.

Making assembly truly language independent would have two significant  
benefits, specifically portability and expanding SCA's relevance.  
Realistically, the best chance of achieving portability for SCA is at  
the assembly level. The further one goes "down" - e.g. into policy,
 
component implementations, and actual application code - portability  
becomes problematic. For example, policy is not likely to be portable  
given the ability to use different policy languages. The Java  
specification also does not address many of the areas required to  
write portable applications such as database access and using managed  
threads. If Java EE is any indicator, achieving portability of  
application code is likely to require years of effort, and even then  
the results are likely to be incomplete. However, in my opinion,  
portability at the assembly level is a realistic goal and should be  
pursued by making it as language independent as possible.

Language independence would also expand the relevance of assembly to  
areas Java EE could never touch. Assembly can be used across a host of
 
proprietary programming languages, essentially providing a portable  
blueprint of systems, regardless of the technologies they run on. In  
my opinion, this may prove to be the most important contribution SCA  
has to make.

Jim


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