A MODULAR APPROACH TO PROGRAMMING DISTRIBUTED REAL-TIME SYSTEMS

Conventional real-time programs associate real-time requirements with individual commands in a program. This approach has three weaknesses. First, it intermixes two different design concerns: functional correct ness and temporal correctness. Second, by mixing real-time requirement s with program statements it makes it harder, and in some cases infeas ible, to specify constraints between objects. Third, it limits the abi lity to independently modify either the timing constraints or the repr esentations of objects. We describe a new approach that separates real -time constraints from functional aspects of an application; real-time constraints are described by synchronization code between the interfa ces of objects. Objects in our system are defined using a real-time va riant of the Actor model. We define a high-level programming language construct called RTsynchronizer, which specifies a collection of tempo ral constraints between actors. Thus, our approach separates what an o bject does from when it does it. Such separation also facilitates the ability to dynamically modify real-time constraints. We illustrate the use of RTsynchronizers by a number of examples and then describe a me ta-architecture that can be used to implement RTsynchronizers. (C) 199 6 Academic Press, Inc.