Active objects in hybrid

Abstract

Most object-oriented languages are strong on reusability or on strong-typing, but weak on concurrency. In response to this gap, we are developing Hybrid, an object-oriented language in which objects are the active entities. Objects in Hybrid are organized into domains, and concurrent executions into activities. All object communications are based on remote procedure-calls. Unstructured sends and accepts are forbidden. To this the mechanisms of delegation and delay queues are added to enable switching and triggering of activities. Concurrent subactivities and atomic actions provided for compactness and simplicity. We show how solutions to many important concurrent problems, such a pipelining, constraint management and “administration” can be compactly expressed using these mechanisms.