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


From: Peter Niblett [mailto:peter_niblett@uk.ibm.com]
Sent: 01 February 2011 16:02
To: Anish Karmarkar
Cc: OASIS Assembly
Subject: Re: [sca-assembly] Private or local channels


I still see a requirement for sc! oping the exchange of events so that it stays encapsulated within a composite. It has hard to develop and test such a composite if there's a risk that its internal components can get bombarded with events from who knows where once it is deployed.  That was my understanding for why we had private channels in the first place.


[MC] Not my understanding of the model we agreed. It will be hard without runtime involvement to make sure events don’t cross these boundaries, and I think that is too huge a burden for the sca runtime.

There are other ways in which you can reference a genuine ex! ternal JMS topic

1. Reference a global channel bound to the JMS topic (global channels seem a much better fit for something that is external to the whole assembly)
2. Bind the producer or consumer directly to the JMS topic
3. Promote the producer or consumer to the composite level, and bind that to the JMS topic.

Of course I could get the functionality I want from private channels in another way if I were allowed to wire producers directly to consumers.

Peter Niblett
IBM Senior Technical Staff Member
Member of the IBM Academy of Technology
+44 1962 815055
+44 7825 657662 (mobile)

From:        Anish Karmarkar <Anish.Karmarkar@oracle.com>
To:        OASIS Assembly <sca-assembly@lists.oasis-open.org>
Date:        01/02/2011 15:02
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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