Abstract not found

Abstract not found

A large number of different models for concurrent object-oriented programming have been proposed. None of this models have received widespread acceptance. In this paper the Simula model of quasi-parallel execution is extended to include concurrency and synchronization. Active objects may execute concurrently and access shared objects without synchronization. Synchronization may be obtained by means of semaphores. In order to avoid explicit low-level manipulation of semaphores, it is possible to build high-level concurrency abstractions that encapsulates and hide the details of the semaphores. A class library may then include abstractions corresponding to commonly used mechanisms like monitor and rendezvous. When these mechanisms are not adequate, it is possible to define new concurrency abstractions. This approach to concurrent object-oriented programming makes it possible to use many different concurrency abstractions within the same language. It is also possible to some ...

Explosive increase in end-user computing on distributed systems requires that end-users develop application software by themselves. One solution is given as a formula of "a domain model j a computation model." This formula implies that one task in a domain model of cooperative work corresponds to one object in a computation model based on an object-oriented model. Application development environment, M-base 1 , supports this formula for cooperative systems such as groupware and work flow systems. At the first stage, the system behavior at a macro level is expressed by using a modeling and simulation tool for constructing a messagedriven model while focusing on message flow. At the second stage, static structure and detailed specifications of objects are expressed in a script language. Communication among objects is performed by a set of messages instead of a message, for implementation of flexible work flow.

Abstract not found