Concurrent Object-Oriented Languages and the Inheritance Anomaly

A survey of concurrent object-oriented languages is presented. The survey is organized around three models: the Animation Model that describes a variety of relationships between threads and objects, an Interaction Model that classi es the possible semantics of invocations and returns between a client object and a server object, and a Synchronization Model that shows di erent ways in which concurrent invocations can be managed by a server. A number of representative languages are brie y presented. The problem of synchronization in concurrent object-oriented languages is considered in detail including a discussion of the inheritance anomaly. A synchronization mechanism, called a behavior set , is shown to avoid this anomaly in certain cases. The implementation of behavior sets in ACT++, an actor-based concurrent programming framework implemented in C++, is described.