RNet: A Hard Real-Time Distributed Programming System

RNet is a high-level programming system for building and executing distributed hard real-time programs. The main objective in developing RNet is to investigate how high-level programming concepts and tools can be used to simplify the real-time programming task. A distributed real-time program in RNet consists of a configuration specification that outlines the structure and real-time properties of the program, and a set of program modules written in a high-level programming language. The RNet configuration system performs a static feasibility analysis of the specifications and handles the construction, distribution, and execution of the program. A debugging and timing analysis system, currently under development and not described here, will be used to measure the real-time characteristics of network resources and the application program, and to perform a validation of the specifications via simulation. The distributed RNet kernel provides run-time support for message-passing and real-time scheduling. The RNet programming model, based on message ports having associated deadlines, provides the programmer with a direct means of expressing a variety of real-time behavioral effects in a way that can be validated. In particular, timing constraints can be used to obtain reliable event synchronization. Some properties that are considered desirable in a high-level distributed real-time programming system are identified. These address issues such as program moduilarity and reconfigurability, timing constraint specification, validation and enforcement, real-time event handling, I/O and exception handling, logical and physical structure specification, and program analysis. The degree to which RNet succeeds in possessing these properties is discussed.