From: Duane Nickull
[mailto:dnickull@adobe.com]
Sent: Wednesday, November 09, 2005
1:49 PM
To: wsrx
Subject: RE: [ws-rx] Issue 050
Jacques:
My $0.02 worth on this topic is that all we
can really do in this spec is to ensure that the RMS’s understanding of
the ordering of messages (as intended by the AS) is conveyed to the RMD.
Anything else is either out of scope or worse, violates opacity, one of
the core tenets of SOA and WS. There are several assumptions that have to
be made in this, but the mechanics of which cannot be placed in the spec.
- That
the AS will accurately convey the proper information to the RMS. We
should not attempt to specify any messages or mechanisms to do that.
- The
RMD will receive and be able to reconstruct the streams as they left the
RMS or in the alternative, throw a fault. This must be fail proof.
Due to the semantics described in our spec, the RMD will be able to
understand the ordering/delivery intentions of the RMS (which we must
assume is in alignment with the AS). The RMD does not see or care
about the RMS- AS relationship.
- The
RMD is able to convey the “ordering intentions” of the RMS to
the AD (based on the fact that we have a mechanism in the WS-RX protocol
to convey it). We should not specify any mechanics/encodings for
this including whether or not messages are delivered in order (our charter
forbids this). What really matters is that the AD has access to the
intentions. If we word this as “messages are transferred
in order..”, that IS a mechanism from RMD to AD and violates our
charter.
Accordingly, a runtime DA is not really
needed. Chris Ferris and I (and others) have been trying to explain
this, perhaps poorly. We have to assume that both the AS-RMS and
RMD–AD relationships are sound but not try to assume any specific
details. It really doesn’t matter since if the intentions of the
service as a whole are not met, the invocation should fail.
Chris states:
“As I have tried,
apparently unsuccessfully, in the past to explain... regardless of the DA
in
force, in effect or observed at the RMD, the source CAN ONLY know which
messages have
been
received. It can make NO assumptions (unless it wants to succumb to the Felix
Unger
ass-u-me
adage) as to which messages have been or ever will be "delivered" to
the AD.”
Any wording such as “…Messages
are “transferred” in order…” specifies an assumption of a specific mechanism behind a
service boundary, something which I do not like. We should not constrain
all applications to serial processing only based on message reception events.
Many, including myself, would probably prefer to architect serial
processing of the message payloads, but not constrain that they have to be
actually delivered in serial order. This is a bad practice as it creates
an unnecessary dependency on the base transport routing between RMD and AD and
also adds a requirement for some form of RM behind the service to detect out of
order messages. A far more elegant solution would be for the RMD to
convey the ordering information to the AD, deliver the messages in whatever
sequence it likes and let the AD use that information to do its’ job or
processing them correctly. We should assume that people implementing this
are not idiots and will take proper precautions in the manner they feel is best
and not constrain behavior behind firewalls.
Duane
From: Jacques Durand
[mailto:JDurand@us.fujitsu.com]
Sent: Tuesday, November 08, 2005
7:05 PM
To: Duane Nickull; Yalcinalp,
Umit; wsrx
Subject: RE: [ws-rx] Issue 050
(assuming this is the right thread for
this... can't say I am as lazy as some Canadians for an excuse ;-)
As far as I can tell, there are two
proposals on the table for i050: both consist of removing DAs from "this"
protocol specification, yet they are very different:
1- Proposal currently logged with the issue def: DAs are simply moved
to another document(s):
(a) Remove
all references to delivery assurances from the WS-RM spec
(b)
Describe, in detail, DA's in the policy spec (since we're adding an Assurances
element to that document anyway).
(c ) Create a new deliverable for the
TC; a profiles document. The profiles would describe how the protocol should be
used to implement the various delivery assurances
2- The one informally proposed in October discussions:
That
any mention of DAs be removed altogether from any doc produced by this TC (if I
interpret well)
I would
consider (2) only if I were convinced that the protocol specification *really* supports the DAs that we are after
all chartered to support, and if these DAs were defined in an unambiguous way
for a starter. Two examples of why I think it is premature to shut down any
talk on DA at this stage:
- I note
that InOrder is defined differently in our charter ("Messages
are transferred in the order in which they are sent") and in our draft ("..delivered
in the order in which they are sent").
I do not consider a charter a precise-enough doc to look for an accurate
definition of what we really are supposed to enable in a final spec. DAs have
to be more accurately defined somewhere else.
- at
this time I'm not convinced that InOrder will work if defined as purely an
RMD/AD contract. For this to work out, more needs to be done, e.g. there must
be a requirement (today absent) for the RMS to assign sequence numbers to
messages in the order they have been submitted (sent), which is an obvious
precondition for the order to be restored on destination side (hint: that looks
to me like an AS/RMS contract...).
Jacques
From: Duane Nickull
[mailto:dnickull@adobe.com]
Sent: Friday, November 04, 2005
4:48 PM
To: Yalcinalp, Umit; wsrx
Subject: RE: [ws-rx] Issue 050
Pure laziness. Rather than make a
new email I simply copied an existing one and replied. While I changed
the thread subject, I did neglect to delete the existing text in the body. It
is gone now.
Most Canadian are lazy. I am no
exception. What can I say ;-)
May I ask why you not support the first
proposed resolution? I would be interested in hearing a counter argument
for keeping it.
Thanks
Duane
From: Yalcinalp, Umit
[mailto:umit.yalcinalp@sap.com]
Sent: Friday, November 04, 2005
4:18 PM
To: Duane Nickull; wsrx
Subject: RE: [ws-rx] Issue 050
I am not sure why this is put
forward in this thread, but
A big -1.
--umit
From: Duane
Nickull [mailto:dnickull@adobe.com]
Sent: Friday, Nov 04, 2005 10:27
AM
To: wsrx
Subject: RE: [ws-rx] Issue 050
After more contemplation, I would like to
suggest we accept Marc's proposal #1 WRT 050. Remove all DA's from the
spec.
Duane