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Subject: Re: [sca-assembly] Private or local channels

I have to disagree again with your point of view, Mike.  In a recursive decomposition model, you don't want to be counting one one of the levels (the Assembler) to be special. 

On 2/1/2011 7:59 AM, Mike Edwards wrote:
OF21390DB4.F567416A-ON8025782A.005682F0-8025782A.005736E5@uk.ibm.com" type="cite">

I tend to sympathise with Anish's view, with the following motivation:

It is the Assembler of a composite who makes decisions about the "local  channels".
In my opinion, if the Assembler has a local channel with no binding, then this is a statement of "privacy"
- only local components can produce/consume events relating to that channel.  However, it may be that
the Assembler decides to apply a specific binding to the Channel, in which case the configuration of that
binding may be specifically designed to allow events to flow to/from other components that might be using
that binding "directly" (eg JMS queue).  

However, this represents an explicit decision of the Assembler,
akin to the Assembler choosing to configure the reference of a component with a binding with a fully
resolved target service address.  It makes the composite less reusable, it makes assumptions about the
"outside world", but it may well serve the purposes of the Assembler very well.

Yours, Mike

Dr Mike Edwards  Mail Point 146, Hursley Park
STSM  Winchester, Hants SO21 2JN
SCA & Services Standards  United Kingdom
Co-Chair OASIS SCA Assembly TC  
IBM Software Group  
Phone: +44-1962 818014  
Mobile: +44-7802-467431 (274097)  
e-mail: mike_edwards@uk.ibm.com  

From: Anish Karmarkar <Anish.Karmarkar@oracle.com>
To: OASIS Assembly <sca-assembly@lists.oasis-open.org>
Date: 01/02/2011 15:08
Subject: [sca-assembly] Private or local channels

During last week's call Peter and I had a little bit of back on forth in
the chat regarding private/local channels. I would like to start a
discussion on it on the ML before I file an issue (or not, depending on
the outcome of the discussion).

Peter has pointed out that line 2815 of our spec says:

"Channels within a composite used as an implementation are private to
the components within that composite. These private channels can only be
the targets for producers existing within the same composite as the
channel. Private channels can only be sources for consumers existing
withing the same composite as the channel. An SCA runtime MAY support
the use of private channels "

Peter's interpretation of this is that composite channels are not
visible to components outside the composite *and* to anyone outside of
the SCA-world. I have a different interpretation of this. I don't think
our spec should talk about what things outside of SCA do or don't do. We
should allow for enough freedom wrt the technology use to implement the
channels. It could be an in-memory channel that is true invisible to
anyone outside the process or a JMS topic, which would have visibility
outside of SCA. We currently allow bindings on a composite channel; that
to me indicates that we intended to allow such variability. If folks
agree with my interpretation, I think we should change the wordings to
replace 'private' with 'local', so as not the give an incorrect impression.



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