Re: [sca-assembly] Issue 37 proposal - a response

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

OK Folks,

This finally stirs me into action.

I have said this on the calls previously,
but I want to get it into an email so that it's there in black & white.

The use case that I see being excluded
by this approach to the Domain is the ability for the configuration
of a Domain level reference which is
a common point for a reference to some service external to the domain
and which carries common configuration
information that is then used by a number of references from 
multiple domain level components.  This
seems a clear use case to me and I don't think that the proposal
deals with it adequately - or rather,
it removes it completely, which leaves me unhappy.


Contribution 1 - contains the Domain
reference
-------------------------------------------------------------------------

<refererence name="DomainRef1"
promotes="component1/ref1 component2/ref2 component3/ref3">
        <interface.wsdl
interface="http://foo.com/bar#wsdl.interface(ref1name)"/>
        <binding.wsdl
uri="http://foo.com/bar/ref1endpoint"/>
</reference>

-------------------------------------------------------------------------

Other contributions....
-------------------------------------------------------------------------

<component name="component1">
        <implementation.xxx
.../>
        <reference
name="ref1"/>
</component>

<component name="component2">
        <implementation.yyy.../>
        <reference
name="ref2"/>
</component>

<component name="component3">
        <implmentation.zzz
.../>
        <reference
name="ref3"/>
</component>

-------------------------------------------------------------------------

The proposal makes Contribution 1 illegal
or "of no meaning", with the result that I am forced to put that
binding
configuration onto all of the component
references directly.  The fact that all 3 components are using the
same
external service is now lost.  Bad
show.  We really lost something here.


==========================================
*WARNING*  Dangerous invention
ahead
==========================================

If folk want to propose an alternative
way of getting this same function, like the use of a "gateway"
component,
then I'd like to see that proposal brought
forward before I'll be happy to approve the current proposal for
Issue 37.

Let me think of something:

<component name="DomainRef1">
        <implementation.gateway
interface=""http://foo.com/bar#wsdl.interface(ref1name)"/>
        <service
name="service"/>
        <reference
name="reference">
         
      <binding.wsdl uri="http://foo.com/bar/ref1endpoint"/>
        </reference>
</component>

implementation.gateway is parameterized
by an interface definition.  This interface defines the interface
which applies to the single (fixed)
service offered by the gateway (name = "service" always) and
the single
reference offered by the gateway (name="reference"
always).  

The implementation.gateway is deployed
as a component into the domain.  Its service can be targeted
by any domain component reference (assuming
interface compatibility).  Its reference can be configured
with any appropriate binding and endpoint
target information.

How "implementation.gateway"
is provided is left to the SCA runtime.  Is a "hop" implied?
 I'd say "no",
but I'm open to persuasion.

I note that in principle the
implementation.gateway could be used as a domain level service as well.
The usecase for this is less strong,
although it could be a way of providing stable external exposure of
services on well-known URIs, independent
of the vagaries of changing internal implementations.

==========================================
End of dangerous invention.


Let's see how you like or dislike that......
  ;-)


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

Anish Karmarkar <Anish.Karmarkar@oracle.com>

20/05/2008 09:03

To	OASIS Assembly <sca-assembly@lists.oasis-open.org>
cc
Subject	[sca-assembly] Issue 37 proposal

Dave and I took an AI to send a proposal for issue
37. This proposal is 
based on what was outlined in previous calls. I haven't had time to 
consult with Dave on this, so all errors are mine.

-----
Deployable composites can contain promoted references and promoted 
services. Promoting a service or a reference in the virtual domain-level
composite has no meaning. When such deployable composites containing 
promoted references and/or promoted services are deployed in the domain
the SCA RUNTIME MUST ignore the promotions. The promoted services and 
references are not part of the virtual domain-level composite.

Note that a deployable composite can contain composite properties, 
components, include elements and wires, which when deployed to the 
domain become part of the virtual domain-level composite.
-----

-Anish
--

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