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

[parkinm at cs.man.ac.uk]

Hi Dominic,

Just some quick questions:

On Aug 27 2007, Dominic Battre wrote:
 
> Thank you very much, Karl, for giving a lot of insight what is behind
> WS-Agreement.
> 
> > Furthermore, 2PC can be synthesized with two WS-Agreement round-trips
> > and an appropriate domain-specific agreement semantics. So, either
> > advance reservation, combined with the right cost/penalty model, or
> > the underlying invitation system can both look like 2PC in practice:
> 
> I tried to digest that and this is what I came up with:
> 
> https://cit-server.cit.tu-berlin.de/trac/negmgr/wiki/TwoPhaseCommit

Between step 5 and 6 of this protocol, how long does the provier wait for a 
response? As there is no facility for the user reject an offer in this 
protocol and let the provider know it doesn't want the advance reservation 
- the provider must specify a time limit to the offer, no? As was said in 
an earlier email - you can't assume agreement is going to happen...

Also, what happens if between step 5 and 6 another user wants to reserve 
the same resources? What does the provider do then?

As I mentioned in a previous email, the provider cannot offer those 
resources to the second user because if the first user accepts and the 
second user acccepts too, there is a problem of overcommitment of 
resources.


> (I used my wiki because it supports tables)
> 
> It would be great, if you could have a brief look at it and tell me
> whether this is what you had in mind.
> 
> 
> If some people want to contribute, I'd be interested in starting to
> write a "Best Practices in WS-Agreement" / "Design Patterns in
> WS-Agreement" / "WS-Agreement cookbook" / ... document.

Yes, I am interested.
 
> This issue of 2PC for example would be a good candidate for such a
> document. I think it would really help if we find a place to collect
> examples, approaches of modeling something, approaches of implementing
> something, ...
> 
> I could easily contribute lots of questions but maybe some answers as 
> well.

Thanks,

Michael.