Efficient Algorithms for Verification of UML Statechart Models

In this article, we present algorithms devised for the automatic verification of UML(Unified Modeling Language) statechart models. The basic algorithm checks the safety property violation during the construction (onthe-fly) of the state space graph and if any property violation is found, it generates a counter example. The second algorithm builds the state space considering only those events, which could lead to the negative behavior of the system. In other words, a set of relevant events is generated first and state space is constructed considering only the state transitions of the objects caused by these relevant events. Thus search space is reduced in both the methods. As a case study, we have verified UML statechart model of the Generalized Railroad Crossing (GRC) system using the proposed algorithms. The safety property “When the train is at rail road crossing, the gate always remain closed” is verified. We could detect property violation in the initial UML statechart model of GRC and eventually it is corrected with the help of the counter example generated by the algorithms. The case study results show that event based verification algorithm yields 59% reduction in the state space for the GRC example.