Local Model Update with an Application to Sliding Window Protocol

Local model update is a procedure whereby a property is found unsatisfied in some model and can be effectively made satisfied in the error reporting counterexample through a series of modifications. With this the counterexample can be reintegrated into the original model to derive a global fix. In this paper we put forward the case for local model update as a method for automatic update. We review theory underlying local model update and introduce the use of a tool lmu for automatically generating candidate updates, looking at general design principles. Finally we present a case study of the update process as applied to an abstraction of the sliding window protocol under a man-in-the-middle attack, showing the modelling process, update procedure and final derivation of a coherant model fix.