Persistence requirement in the WS-RM specification

[<magdolna.gerendai@nokia.com>]

Hi all,

I know, that you had a long discussion yesterday about the persistence requirement in the WS-RM specification, and I would like to add my view to this picture. I'll participate on the today's meeting via telcon too.

The reliability itself from engeneering point of view means at least two things:
- a protocol between parties, which determines the informations exchanged on the wire and the description of the necessary or possible steps they have to or may do to follow the state transitions during the communication. 
- capabilities of the parties, which can be used to maintain the state transitions of the communication.

There are different, valid use cases, which obviously show, that they require different, scalable reliability levels according to the  application environment and capabilities of the participants. We can not say, that there is THE reliability, which mandates a capability requirement, the persistence, as no one can say, that there is THE security, which has to provide all levels of security, including authentication, integrity, confidentality, etc.. We can not exclude from the  deployment of the WS Realibility the devices, which are not capable to have persistent storage and even may not require that level of reliability either. Let the application environment decide, how strong reliability they want or able to use.
  
There are some reliability levels identified (at least):
- communication reliability
- limited crash tolerance reliability
- crash tolerance reliability
- crash tolerance reliability with state synchronization
- ...
and I think, no one can say, that any of them has no value.

Just very shortly an explanation, without the demand of the perfect definition:
- Communication reliability: this is a low level reliability, because it assumes, that the parties are not crashed or swithed off during this communication, e.g. no need to store persistently any message context.
- Limited crash tolerance: this is a next level reliability, which may ensure, that the communication parties are able to give some limited error (status) indication about the previous state of the communication.
- Full crash tolerance: this is the higher level reliability, which the parties can provide for each other saving the full message context persistently...

The introduction of the reliability levels in the specification means, that we insert some clarifications/descriptions, which state transitions can not be followed, what are the error cases, which they can not handle, and specify some new Fault codes for the indication of the inconsistencies on the wire.

And last, but not least: there are two, published reliability papers (private specifications) re the WS reliability area, the  WS-Acknowledgement and the WS Reliable Messaging Protocol. The first one requires the persistence only for the messageID (though the persistence is defined in a large scale) and the second one doesn't mention persistence or store of any data at all.

Again, WS Reliability specification, standardized by this TC, should be intended to a large scale of possible deployment. I hope, it will happen.

Thanks.

br,
Magdolna