An Object Model for Distributed and Concurrent Programming Based on Decomposition

Many of today s object models represent parallelism and distribution inadequately because these models grew out of sequential object oriented languages In this paper we develop a model that is directly derived from an abstract but very simple and compact de nition of the object oriented paradigm It is shown how inter object and intra object concurrency arise naturally from this paradigm The decomposition hierarchy plays a central role in the model It is the logical com munication system topology The position of an object in the hierarchy determines a unique object identi er This enables us to refer to objects prior to their existence and to store object references in the persistent database Clustering of objects based on the hierarchy allows the e cient implementation of persitent storage mechanisms The methods of an object and its instance variables are represented as subobjects in the decomposition hierarchy Parameters to methods and local variables are in turn subobjects of the method objects This uni ed representation simpli es the model and has a signi cant impact on the message invocation process We develop a scheme for our model that allows recursive and concurrent invocations of methods