Integrating concurrency and object-orientation using boolean, access and path guards

Inheritance Anomaly is considered as a major problem in integrating object-orientation and concurrency. The anomaly forces redefinitions of inherited methods to maintain the integrity of concurrent objects. In this paper we discuss how the use of boolean, access and path guards attached to methods solve the problem of inheritance anomaly. Synchronizationusing boolean guards have known to be free of inheritance anomaly caused by partitioningof acceptable states. However, they cause anomalies from history sensitivity. We solve this using path guards. Path guards are similar to path expressions in the sense that both express the execution pattern of methods. However, while a path expression independently specifies the synchronization of a collection of methods, a path guard is attached to a method and it specifies the history of execution sequence(s) acceptable for executing the current method. Path expressions have been shown to cause inheritance anomaly, on the other hand, we will show that path guards form a solution to the problem.