RE: [ws-rx] PR035, PR009, PR020: DA defs

[Stefan Batres <stefanba@microsoft.com>]

Matt,

Thanks for putting this together. I've inlined a couple of comments.

--Stefan


-----Original Message-----
From: Matthew Lovett [mailto:MLOVETT@uk.ibm.com]
Sent: Thursday, January 25, 2007 5:36 AM
To: ws-rx@lists.oasis-open.org
Cc: Durand, Jacques R.
Subject: Re: [ws-rx] PR035, PR009, PR020: DA defs

Hi all,

Following on from the discussion about using "deliver" rather than
"process to conclusion", here are some definitions that Peter and I have
worked on. We believe these definitions help define the end-to-end DA, as
they include the RMS behaviour.

--

wsrmp:DeliveryAssurance

When applied to an RM Destination, this element defines a policy assertion
that identifies a requirement on RM Sources. Any RM Source that transmits
messages to this RM Destination SHOULD conform to the requirement
expressed by this assertion. Conversely, when it is applied to an RM
Source this assertion identifies a requirement on RM Destinations. Any RM
Destination that receives messages from this RM Source SHOULD conform to
the requirement expressed by this assertion.

wsrmp:AtLeastOnce

Each message is to be delivered at least once. The requirement on an RM
Source is that it SHOULD retry transmission of every message sent by the
Application Source until it receives an acknowledgement from the RM
Destination. The requirement on the RM Destination is that it SHOULD retry
delivery to the Application Destination of every message that it accepts
from the RM Source. There is no requirement for the RM Destination to
apply duplicate message filtering.

[SB] I think there should be a requirement to indicate an error if the assurance
can't be met.

wsrmp:AtMostOnce

Each message is to be delivered at most once. The RM Source MAY retry
transmission of unacknowledged messages, but is NOT REQUIRED to do so. The
requirement on the RM Destination is that it MUST filter out duplicate
messages, i.e. that it MUST NOT redeliver any message.

[SB] I find "that is MUST NOT redeliver any message" confusing. The requirement
is to filter out duplicates that arrive on the wire. But we can't forbid redelivery
of a message that arrived only once or for which duplicates have been eliminated.
e.g. RMD delivers message to AD in the context of a local atomic transaction that
gets rolled back, this text seems to say that the message should not be redelivered.

wsrmp:ExactlyOnce

Each message is to be delivered exactly once. The requirement on an RM
Source is that it SHOULD retry transmission of every message sent by the
Application Source until it receives an acknowledgement from the RM
Destination. The requirement on the RM Destination is that it MUST filter
out duplicate messages, i.e. that it MUST NOT redeliver any message.

[SB] Same comments apply.
--

Some additional comments:

Doug pointed out that we talk about the RMS and RMD here, but that the
wsrmp spec doesn't quite call out where the RMS and RMD are. For example,
if a WSDL output message is decorated with the RM assertion + a DA, we
would expect the server-side RMS to exist and do it's part, and similarly
the client side RMD has a role to play. I think that this is a separate
issue, and needs a bit of discussion, but the text for the DAs should be
ok however we resolve that.

Jacques: I hoped to get this out to you earlier so you could see our
thought process, but I'm running out of time before the call. I'm sorry
that time got away from me!

Thanks

Matt