After talking about this with various people, it
seems the resolution may now be clear due to issue 79, but it is also not
what it should be.
There is no really strong reason why we do not
allow PREPARE_INFERIORS to an Atom Coordinator. Although partial preparation
can only everntually lead to general preparation and confirmation (or
cancellation), the possibility of spontaneous PREPARED's arriving (triggered
by application messages), and the availaibility of REQUEST_INFERIOR_STATUSES
means that partial preparation is possible with an atom - just that (at
present) the standard control relatinship don't allow it to be
induced. It's possible to imagine scenarios where an application
want to force some Inferiors to determine if they could go to prepared
state, before performing further work. It's more difficult to explain why
you can't do it than to allow it.
The same argument does not apply to
CANCEL_INFERIORS, since if one inferior is cancelled, they are all going to
be, and the only possible next message is
CANCEL_TRANSACTION.
If
this is followed, then
Suggested solution:
Clarified by solution to issue
79
In
PREPARE_INFERIORS, delete the phrase ", but only if it is a Cohesion Composer, " in the first line, and the two (Composer)
after Decider..
Also change the description for the Coordinator in
the role section (the lists of what is sent and received will be updated by
issue 61)
Peter
believe this issue was
resolved by the agreed solution to issue 79 - with the normalisation of
the message set the original ambiguity has gone:
PREPARE is sent from Superior to Inferiors, whether they are
Participants or sub-Coordinators (or sub-Composers)
PREPARE_INFERIORS is sent from Terminator to Composer' (as a
Decider)
There is no direct equivalent message sent from a Terminator to a
Coordinator (as said in the November messages, if you want to prepare a
Coordinator, presumably you want to confirm it, so you jump straight ahead
to CONFIRM_TRANSACTION).
Proposed solution
Resolved by solution to issue 79
Peter
------------------------------------------
Peter
Furniss
Technical Director, Choreology Ltd
web: http://www.choreology.com
email:
peter.furniss@choreology.com
phone: +44 20 7670 1679
direct:
+44 20 7670 1783
mobile: 07951 536168
13 Austin Friars, London EC2N
2JX