Bill, in order to make things symmetrical with
pass-by-value and pass-by-reference, I think it makes sense to ensure that
setContents "throws" an appropriate exception (i.e., returns an error message)
if an attempt is made to write to an immutable pass-by-reference
context (assuming we stick with these course grained get/set
operations).
Mark.
---- Mark Little, Chief Architect,
Transactions, Arjuna Technologies Ltd. www.arjuna.com
----- Original Message -----
Sent: Friday, February 13, 2004 6:00
PM
Subject: RE: [ws-caf] context sharing
(issue 46)
Mark,
As
the person who raised this issue your proposal is acceptable to
me.
=bill
Issue 46 (and a related issue from Peter
Furniss) is about the concurrency control implications of allowing a mutable
context to be shared, either when it is passed by reference or
passed by value. To be honest, when writing the original specifications
we deliberately didn't address this because it isn't easy (!) but also
because I don't believe there's a clear solution. Maybe there will be in a
couple of years once people start to use implementations of WS-Context once
it becomes a standard, but at the moment I don't think it's clear
cut.
My preference on this issue would be two
fold:
a) explicitly mention this potential issue in
the specification and leave it up to the implementation as to how (and if)
it wants to tackle it,
and
b) add an "immutable" or "readonly" flag to the
context schema (default could be true), which means that the context cannot
be augmented by application-level Web services. All other augmentation
happens by ALS-es under the control of the Context Service
anyway.
Mark.
---- Mark Little, Chief Architect,
Transactions, Arjuna Technologies Ltd. www.arjuna.com
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