Toward an Effective Execution Policy for Distributed Real-Time Embedded Systems

Thomas Huining Feng, Edward A. Lee, Hiren D. Patel, and Jia Zou

in Proceedings of the 14th IEEE Real-Time and Embedded Technology and Applications Symposium (RTAS 08), Work-in-Progress Session, St. Louis, MO, USA, Apr 2008.




Zhao, Liu, and Lee have proposed using a discrete-event (DE) model of computation as a programming model for distributed real-time embedded systems. The advantage of using DE is that it provides a semantic foundation that is simple, time-aware, deterministic and natural as a specification language for many applications. This programming model is based on a carefully chosen relationship between DEs model time and real time (physical time). We define here a criterion that preserves conservative execution (thus not requiring backtracking) while allowing for concurrent and distributed execution. The classic Chandy and Misra technique is one execution policy that satisfies the criterion, but the criterion explicitly allows many other alternatives. We discuss alternatives that offer more concurrency than Chandy and Misra and that exploit time synchronization to eliminate the need for null messages.