[GRAAP-WG] Modification to the wiki Page on Renegotiating an established Agreement

[Dominic Battre]

Hi Toshi,

>> For that reason I mentioned the "superseded by" information that could
>> be added to the context. A third party might need to check whether the
>> SLA is superseded by another SLA periodically. Kind of ugly...
> 
> I see. I had been wondering what you meant by "superseded by"..
> It might be necessary to have a Notification sent to all the bodies using
> the old EPR...

Either that or to forward all requests transparently in the Agreement
webservice. (i.e. if a message is sent to the old agreement it is
automatically forwarded and answered to/by the new agreement).

In case of the notification, we have again the problem that the delay of
delivering the notification means that some parties are unaware of the
new state for some time.


>> AI ------ 1. please change SLA like this ------> AR
>>                                 2. AR decides that it can change SLA
>>                                 3. AR calculates price of modification
>>    <----------- 4. new offer ------------------
>> 5. AI decides whether change is worth the price
>>    --------- 6. confirmation/rejection --------->
>>
> 
> I agree that this is more beautiful.
> OTOH I think that this raises the issue related to two phase commit protocol
> that had been discussed
> for a long time and in a heated manner by quite a number of people (before
> my time actually) 
> and finally got rejected in the original WS-Agreement protocol.
> 
> I  am a bit afraid of waking the sleeping monster, but I welcome people's
> comments..

Yes, I remember the discussion in Leeds. But on the other hand:

"A WS-AGREEMENT BASED RESOURCE NEGOTIATION FRAMEWORK FOR MOBILE AGENTS"
by D.G.A. Mobach, B.J. Overeinder, and F.M.T. Brazier introduced the
additional commit and argues why it is important.

Oliver's WSAG4J has a commit message in the NegotiationAgreement
interface (I don't know whether it is required or whether it is
implemented for some historic reasons).

Our Negotiation Manager implementation (online since a few days ago:
https://cit-server.cit.tu-berlin.de/trac/negmgr/wiki) needs it.

So, yes, there are problems but it looks like a lot of people want to
have this extra commit message. Are there any written records on the
pros and cons of having the 2PC?

Best regards,

Dominic