[graap-wg] minutes from 4/5 telecon

[Karl Czajkowski]

On Apr 06, Asit Dan modulated:
> 
> Karl,
>    It is understood that receiving a termination message (and upon
> provider acknowledgement),  i) an agreement state transitions from a
> "Pending" to "PendingAndTerminating", and ii) the termination of
> service/agreement is not instantaneous (as you have elaborated).      
> 
> What we are trying to resolve here are the semantics of the states
> "PendingAndTerminating"  and "ObservedAndTerminating", i.e., what are
> the obligations in delivering (service and) service quality, while an
> agreement is being terminated.   Clearly, the options are
> 
>                      a) No further obligations in delivering service
> quality (these states explicitly capture start of termination process,
> and the only difference between the above two states are historical,
> i.e., the state at which the termination message is received).


I think there is another semantics of concern about the implied
obligations, i.e. the "payment" or "penalties".  Let us assume in all
cases that no service delivery guarantees will be expected once the
client sends the terminate request.

The issue I am trying to raise is that it is not just an atomic "state
at which the termination is received".  If I, as a broker, am in the
process of computing acceptance when the termination is received, I
would like to reserve the right to decide LATER whether I had accepted
or rejected the agreement.  I cannot make this decision
instantaneously but must synchronize with a potentially complex
brokering process.  If allowed to by the specification, I could return
immediately with the state I know (PendingAndTerminating) and still
would be able to enter other states to reflect what happened.

So, PendingAndTerminating->ObservedAndTerminating->Terminated would
mean that I have decided, due to the non-deterministic things I was
doing as a broker, that I was not able to complete your terminate
request before accepting.  I will bill you as having terminated an
accepted agreement, i.e. in order to cover my own obligations with the
services I was brokering (who may have accepted my offers before I
could request termination).

On the other hand, PendingAndTerminating->Terminated would mean that I
have decided that I was able to complete your terminate request before
accepting.  I will bill you as having terminated a pending agreement,
i.e. I do not have to cover obligations with brokered services because
I either terminated them early or never even got around to making
offers.

The issue is that at the time I, the broker, receive your terminate
request I do not really know the distributed state of my own brokering
process and I cannot tell you whether I will have to go into
ObservedAndTerminating or not.  So, if we do not allow the
PendingAndTerminating->ObservedAndTerminating transition, then I
cannot respond to show any "terminating" state until I am able to
synchronize my distributed process and make this determination.

If you buy any of this, I think there is also an issue of having
distinct final states (maybe sub-states?) for Terminated to encode the
history of whether the agreement had been accepted or not.


karl

-- 
Karl Czajkowski
karlcz at univa.com