Loosening the notions of compliance and sub-behaviour in client/server systems

In the context of “session behaviors” for client/server systems, we propose a weakening of the com- pliance and sub-behaviour relations where the bias toward the client (whose “requests” must be satisfied) is pushed further with respect to the usual definitions, by admitting that “not needed” out- put actions from the server side can be skipped by the client. Both compliance and sub-behaviour relations resulting from this weakening remain decidable, though the proof of the duals-as-minima property for servers, on which the decidability of the sub-behaviour relation relies, requires a tighter analysis of client/server interactions.