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Subject: Re: [sca-assembly] Fw: [sca-assembly-comment] NEW ISSUE: (1.2) Promotionof consumers and producers undermines composability

Follow up....

I've just posted to the OASIS documents repository a proposal for ASSEMBLY-227.

I posted in PDF and Word format:

These documents are *not* in anything close to final form:
  • OpenOffice did a number of things to slightly mangle the word document
  • We need new pictures to show the new channel promotion notion.  I've included my notion of what it would look like below, in the hopes that it will help, although I should add that so far within TIBCO, I've gotten the some disagreement about the proposed artwork.
  • I haven't vetted the schema changes.
  • Obviously this is still a fork of the current spec, based off of the copy that Anish started from.
However, before I spent many hours trying to get everything perfect, I figured I should at least know whether the intent is even close to acceptable to the TC.


P.S. My current conception of a channel might look like - see diamond at the bottom edge of the component.

On 04/09/2010 01:19 AM, Mike Edwards wrote:
OFE5388E5F.52899241-ON80257700.002DAACF-80257700.002DB307@uk.ibm.com" type="cite">

Forwarding to the main sca-assembly TC list....

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

----- Forwarded by Mike Edwards/UK/IBM on 09/04/2010 09:18 -----
From: Eric Johnson <eric@tibco.com>
To: sca-assembly-comment@lists.oasis-open.org
Date: 08/04/2010 18:18
Subject: [sca-assembly-comment] NEW ISSUE: (1.2) Promotion of consumers and producers undermines composability

Target: sca-assembly-1.2-spec-wd01.doc

Title: Promotion of SCA consumers and producers undermines composibility


In the assembly 1.2 WD 01, consumers and producers are identified as part of the "component type" of a component, whereas "channels" are limited in scope to the boundaries of a composite.  This is contrary to the rest of SCA, where the indication of the communication between components surfaces in the component type, currently as a service or reference.  When needed, services or references can establish concrete bindings, but otherwise communication needs are exposed at the boundary of a composite.  In the case of producers, consumers, and channels, not only can bindings be applied, but also "targets", which then either hide endpoints within a composite, or expose them globally as part of the "global domain."

This makes composition of applications using eventing more difficult.

Further, although producers and consumers can refer to the same target, this is an awkward way for these two constructs to establish that they intend to operate on the same "destination".  When building a composite the composite developer may wish for one component to produce for a channel, and a different component to publish on the same channel, and then promote the combination of producer and consumer.  If the developer only promotes the consumer, or only promotes the publisher, that would be misleading to the composites using that component.  Perhaps it is even an error.

Here, then, are two problems:
  • "target" channel references are a weak way to couple the use of the same destination.
  • target channel references can be to a domain channel, thus undermining composability - either by collisions in the naming of target channels, or by forcing special knowledge of which channels are used where.

Instead of promoting consumers and producers, promote channels.  Move the filter and eventType information on consumers and producers into the channel.


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