Modular Multiprogramming

多道程序设计研究的两个主要目标是：(1)孤立地设计和理解程序的模块(例如进程或数据对象)，而不考虑其他模块的干扰；(2)在具有细粒度交错的独立处理器上实现模块，以使处理器不会长时间被锁定访问公共数据。此外，有必要设计一种模型，消除计算和通信之间的区别；特别是，关于接口的设计和推理方法应该与在网络节点进行计算所采用的方法没有区别。该项目基于这样的假设，即为数据库、面向对象的编程和反应式系统的设计开发的许多编程概念可以统一到满足预期目标的分布式程序的紧凑模型中。在过去，通过使用各种同步机制(锁或信号量、关键区、监视器和通信)来限制模块之间的干扰。在本项目中，除了过程调用之外，该模型没有构建特定的通信或同步机制。然而，使用受限或非受限通道、信号量和对共享内存的访问的传统通信方案可以被编码为模块。该项目使用两种不同的过程来对编程的顺序和并发方面进行建模。编程模型允许这两种类型的过程之间有纪律的交互。该研究旨在：(1)开发模型，特别是用于模块的动态创建；(2)在现有语言的基础上实现该模型；(3)开发适当的形式化来指定和验证程序的属性。

Two major goals in multiprogramming research are: (1) to design and understand the modules (e.g., processes or data objects) of a program in isolation, without considerations of interference by the other modules, and (2) to implement the modules on separate processors with a fine grain of interleaving so that no processor is ever locked out of accessing common data for long periods of time. Further, it is essential to devise a model in which the distinction between computation and communication is removed; in particular, the methods for designing and reasoning about the interfaces should be no different from those employed for the computations at the nodes of the network. The project is based on the hypothesis that many of the programming concepts developed for databases, object-oriented programming and designs of reactive systems can be unified into a compact model of distributed programs that meets the desired goals. In the past, much effort has gone into limiting interference among the modules by employing a variety of synchronization mechanisms: locks or semaphores, critical regions, monitors and communication. In this project, no specific communication or synchronization mechanism, except procedure call, is built into the model. Yet, the traditional schemes for communication using bounded or unbounded channels, semaphores, and accesses to shared memory can be encoded as modules. This project uses two distinct kinds of procedures, to model sequential and concurrent aspects of programming. The programming model allows for disciplined interactions between these two types of procedures. The research seeks to: (1) develop the model, in particular for dynamic creations of modules (2) implement the model on top of an existing language, and (3) develop the appropriate formalism to specify and verify the properties of programs.