Re: [sca-assembly] [ISSUE 157] Make support for constrainingType anoptional compliance point - Proposal

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

Anish,

I take the view that constrainingType
is mostly about design time.

So to me, if a composite happened to
contain references to constrainingType, a runtime that
does not support constrainingType should
not reject that composite, since in the 99% case, 
the composite is valid and should run
perfectly successfully.  I see little advantage in rejecting
such composites, other than to cause
folk to rip out constrainingType markings from composites
if they would not run.  This would
not favour the use of constrainingType.

Basically, I see this behaviour as treating
constrainingType as an extension, where there is no
requirement for the runtime to understand
the extension.  I think that this is the right approach.


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:	Anish Karmarkar <Anish.Karmarkar@oracle.com>
To:	Mike Edwards/UK/IBM@IBMGB
Cc:	OASIS Assembly <sca-assembly@lists.oasis-open.org>
Date:	29/09/2009 07:19
Subject:	Re: [sca-assembly] [ISSUE 157] Make support for constrainingType an optional compliance point - Proposal

---

The issue [1] states:
"I'd like to assert that there may be many different ways to capture
the 
top down design of a component or more importantly the design of a set
(or assembly) of components."

No doubt, top-down can be accomplished in variety of ways that go beyond
the SCA Assembly spec. But IIRC, the discussion around those ways has 
always been about creating some kind of template that the assembler is
going to later edit to fill in details. I think there is a significant
difference between non-deployable/non-conformant templates and "typing"
support in SCA runtimes. The current design of constrainingType provides
a way for the top-down designer to design a contract that is enforced by
the runtime. There is a significant value in that. I understand that 
taking the optional route is sometimes (always?) a nice compromise in a
design-by-committee venue, but I think in this case, it significantly 
reduces the value of the feature. In the same sense that making 
recursive composition optional would undermine the value of that feature.

Even though I don't like the proposal, I do have a question about it:
Why does the proposal make it OK to ignore constrainingType when not 
supported? I would have thought that it would be the opposite. 
constrainingType is part of the contract, if the runtime doesn't support
it, it should reject the artifact that contains it rather than ignore it
and break the contract.

Thanks.

-Anish
--

[1] http://www.osoa.org/jira/browse/ASSEMBLY-157

Mike Edwards wrote:
> 
> Folks,
> 
> Here is a proposal to resolve Issue 157:
> 
> http://www.oasis-open.org/apps/org/workgroup/sca-assembly/download.php/34342/sca-assembly-1.1-spec-cd03-Rev2%2BIssue157.pdf
> 
> http://www.oasis-open.org/apps/org/workgroup/sca-assembly/download.php/34341/sca-assembly-1.1-spec-cd03-Rev2%2BIssue157.doc
> 
> 
> 
> 
> 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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