Real-time systems are computing systems that must react to the dynamic environments under timing constraints.  Real-time systems are pervasive since many societal-scale infrastructure systems, such as manufacturing systems, power networks and transportation systems, require real-time computing. The correctness of the systems depends on not only how correct the computation is but also how accurate the computation can satisfy the timing constraints.  However, most of the real-time systems are still designed and implemented using low-level programming and empirical techniques. The resulting real-time systems produced can be highly unpredictable. The consequences of a failure can be catastrophic, such as the accidents happened on the Mars Polar Lander, the Ariane rocket and the Patriot Missile system.

This course focuses on the analysis and design of real-time systems. The course covers topics on system modeling using the tagged signal models and timed models of computation [1], specifications and scheduling techniques for real-time tasks [2], simulation and verification of real-time systems, software architecture and language for constructing real-time systems [3,4,5]. Special attention is paid to computational and simulation tools for real-time systems. Applications ranging from robotics, embedded control systems, drive-by-wire systems, space missions, telecommunication systems, industrial automation, and middleware software systems will be covered. 

[1] E. A. Lee and A. Sangiovanni-Vincentelli, "A Framework for Comparing Models of Computation," IEEE Trans. CAD, Vol. 17, No. 12, December 1998.

[2] Giorgio C. Butazzo, Hard Real-Time Computing Systems, 2nd Edition, Springer, 2005.

[3] H. Kopetz, “The Time Triggered Architecture,” Proceedings of the IEEE,  Vol. 91, No. 1, January 2003.

[4] Thomas A. Henzinger, Benjamin Horowitz, and Christoph M. Kirsch, “Giotto: A Time-Triggered Language For Embedded Programming,” Proceedings of the IEEE,  Vol. 91, No. 1, January 2003.

[5] B. Horowitz, J. Liebman, C. Ma, T. J. Koo, A. Sangiovanni-Vincentelli, S. Sastry, “Platform-Based Embedded Software Design and System Integration for Autonomous Vehicles,” Proceedings of the IEEE, Vol. 91, No. 1, January 2003.

Useful Links on this webpage has been updated. 

Please read Chapter 1 and 2 for the background on Real-Time Systems.

Please read the information regarding the mini-project. The due date of the project is 2/28/04. There are three robots available  so please form into three groups. For each group, please submit 1) the name of your group and the list of your group members by  1/26/2005.

To read more about models of computation, please go to the Useful Links and read a chapter on Models of Computation from Embedded, Everywhere, National Research Council.

Joseph Sifakis is CNRS researcher and the Director of  the Verimag laboratory (http://www-verimag.imag.fr/), in Grenoble, France. He studied Electrical Engineering at the Technical University of Athens and Computer Science at the University of Grenoble. Joseph Sifakis worked on both theoretical and practical aspects of Concurrent Systems Specification and Verification. He contributed to the development of the state of the art in verification methods and tools by model-checking for both untimed and timed systems. His current research interests include modeling, design and analysis of real-time systems with a focus on composability and compositionality. (Further information: http://www-verimag.imag.fr/~sifakis/ ) Joseph Sifakis is a member of the editorial board of several journals, co-founder of the CAV (Computer Aided Verification) conference and a member of the Steering Committee of the EMSOFT (Embedded Software) conference. He is the recipient of the CNRS Silver Medal in 2001. Joseph Sifakis is the scientific coordinator of the European Network of Excellence ARTIST2 on Embedded Systems Design. (Further information: (http://www.artist-embedded.org/Overview/ )

Modeling Real-time Systems Joseph Sifakis Verimag, Grenoble, France Sifakis@imag.fr Modeling real-time systems raises non trivial problems for the definition of usable modeling languages and the application of model-based development approaches. We identify key problems and present corresponding research directions for the incremental construction of timed models for real-time systems. We present a framework that may provide some solutions and an associated methodology for model construction. Timed models of real-time systems are obtained by adding timing constraints to their application software. These constraints take into account execution times of atomic statements, the dynamics of the external environment, as well as quality of service requirements. The framework combines two kinds of composition operators for timed components: • Restriction operators which are unary operators parameterized by a safety property. Their application on a component restricts its behavior so as to meet the associated property. Dynamic priorities correspond to a class of restriction operators which preserve deadlock-freedom of their arguments. • Parallel composition operators, parameterized by interaction models. These models describe interactions between actions offered by the composed components and their associated synchronization requirements. We show that the combination of parallel composition and restriction operators allows compositional modeling of real-time systems, in particular of aspects related to heterogeneous interaction and execution, resource sharing and scheduling. Scheduling policies are modeled by dynamic priorities. The framework supports composition of scheduling policies and provides compositionality and composability results for deadlock-freedom of scheduled systems. We show applications of these results, including model-based development of applications in Esterel and real-time Java, as well as a partial implementation of the framework in Verimag’s IF toolset.

References Joseph Sifakis “Modeling real-time systems--challenges and work directions” EmSoft01, LNCS 2211, Tahoe City, October 2001. J. Sifakis, S. Tripakis, S. Yovine "Building models of real-time systems from application software" Proceedings of the IEEE, Special issue on modeling and design of embedded systems, 91(1):100-111, January 2003. K. Altisen, G. Goessler, J. Sifakis “Scheduler modeling based on the controller synthesis paradigm” Journal of Real-time Systems, Vol. 23, pp.55-84, 2002.

G. Goessler, J. Sifakis "Composition for component-based modelling", FMCO02, LNCS 2852, pp. 443-466. E. Closse, M. Poize, J. Pulou, J. Sifakis, P. Vernier, D. Weil S. Yovine “ TAXYS : a tool for the development and verification of real-time embedded systems ” CAV01, LNCS 2102, Paris, July 2001. C.Kloulinas, C. Nakhli, S. Yovine “A methodology and tool support for generating scheduled native code for real-time java applications” EmSoft03, LNCS 2855, pages 274-289. Philadelphia, October 2003. The IF toolbox http://www-verimag.imag.fr/~async/IF/index.shtml.en