Concurrency within objects: layered approach

Object-oriented systems have provided a new methodology for decomposing problems. They have also brought out the issue of the specification of concurrency in a more structured manner. The paper shows how the Parallel Objects (PO) model addresses the problem of supporting concurrency. PO is a parallel object-oriented model. Any entity/object is capable of independent execution and in addition several concurrent activities can exist within the same object. In fact, as a feature distinguished from other concurrent object systems, PO does not strive to obtain intra-object sequentialization. In PO, the specification of concurrency can take advantage of a layered approach. Depending on user skill, the system requires more or less deep insight of PO to specify concurrency. A novice user can derive the specification of object concurrency from the PO environment. This approach stresses the reuse principle typical of object systems, i.e., inheritance. The PO environment makes it possible for skilled users to investigate complex concurrency policies and their performances for the same application. © 1991.