In the conventional protocol synthesis, it is generally assumed that primitives in service specifications cannot be executed simultaneously at different Service Access Points (SAPs). Thus if some primitives are executed concurrently, then protocol errors of unspecified receptions occur. In this paper, we try to extend a class of service specifications from which protocol specifications are synthesized by the previous methods. We first introduce priorities into primitives in protocol specification so that it always selects exactly one primitive of the highest priority from a set of primitives that can be executed simultaneously, and executes it. Then, based on this execution ordering, we propose a new protocol synthesis method which can avoid protocol errors due to message collisions, communication competitions and so on. By applying the proposed synthesis method, we can automatically synthesize a protocol specifications from a given service specification which includes an arbitraty number of processes and allows parallel execution of primitives.

Responsive protocols are communication protocols which ensure timely and reliable recovery when error events occur. Protocol synthesis for design of responsive protocols is to derive a protocol specification based on a service specification. In the previous methods, if the service specification includes simultaneous transmission of primitives from a high layer to a low layer through different service access points, then the derived protocol specification includes protocol errors of unspecified reception caused by message collisions. Also, they only includes a recovery function such as retransmission of messages. This is not enough for recovery from abnormal states due to coordination loss. This paper extends a class of derived protocol specifications to include message collisions which usually occur in real communication protocols. Furthermore, this paper proposes a new method for synthesis of a responsive protocal specification derived from a service specification such that the derived protocol specification is free from protocol erros of unspecified receptions caused by message collisions and includes two recovery functions: message retransmission and checkpoint restart functions.