Preserving consistency of runtime monitors across protocol changes

Protocols governing communication among the components of a complex system are frequently changed during the design process. To enable faster verification turnaround time, it is important that the existing verification infrastructure continues to be consistent with the changed protocol. In this paper, an approach to identify the effects of protocol changes on runtime monitors is proposed. Runtime monitors are commonly used to observe and verify the dynamic protocol behaviors. Protocols as well as the monitors are modeled using communicating finite state machines. Addition/deletion/replacement of transitions in one or more protocol components may result in similar changes to the monitor transitions. A notion of consistency of a monitor relative to a protocol is introduced. Conditions under which a protocol change necessitates a change to the monitor to preserve relative consistency are identified. Automatic procedures to synthesize new monitors that are guaranteed to be consistent with the changed protocol are described.