I have been looking at the SCA Transaction spec and I have noticed some
difficulties reconciling the transaction intent descriptions with the
capabilities of the policy framework.
1) The SCA Transaction spec has several sets of mutually-exclusive
intents: managedTransaction and noManagedTransaction, propagatesTransaction
and suspendsTransaction, transactedOneWay and immediateOneWay. In the
policy framework all intents are additive and there is no concept of
exclusive intents. I know this problem was discussed in the OSOA Policy
working group but it was left unresolved in the published specs. I think
there needs to be some extension to the policy framework implementation to
handle exclusive intents.
2) The transactedOneWay and immediateOneWay intents are unique in that
they apply to services and references but are classified as implementation
intents (rather than interaction intents). What this means is that the
intents specified at each end of the wire having no bearing on each other.
A reference might use transactedOneWay while the service uses
immediateOneWay or vice versa. This conflicts with the following statement
in section 1.4.10 of the SCA Policy Framework:
"If the element is a binding instance and its parent element
(service, reference or callback) is wired, the required intents of the other
side of the wire may be added to the intent set when they are available.
This may simplify, or eliminate, the policy matching step later described in
step C."
I think this statement needs to be clarified to say that only interaction
intents are to be copied. It also means there needs to be some extension to
the intent definition that indicates whether an intent is an interaction
intent or not.
I also found a minor problem in the Tuscany implementation of the policy
framework. In the process of trying to find a policy set that matches the
required intents, the code removes intents from the intent attach point that
it finds in a bindingType or implementationType mayProvide list. I'm not
sure how the binding or implementation can provide the intent if it has been
removed. I think the code needs to be changed to preserve these intents in
the intent attach point and just skip over them when looking for matching
policy sets.
Greg Dritschler
