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Designing the Server

Introduce variable wait to record deferred requests:

ServerC,R(server, client, counter, wait) :<=>    exists i in [1,C]:       or          ...          receivei(server, request)  /\ count <=0  /\              wait' = wait[i |-> true]  /\              changed(server, wait)

Need to guarantee progress:

InvariantC,R(pc, server, client, counter, wait) :<=>

and

...

exists j in [1,C]: wait[j] =>       Grant only deferred as long as necessary.

count = 0

Need to maintain refined invariant.