Compositional design and analysis of distributed, cyclic, and adaptive embedded real-time systems

Abstract

Embedded systems are computer systems that are deeply integrated in and interact with the physical world. The physical world often imposes strict timing constraints on these systems. Therefore, the correct operation of such systems depends not only on the values of the produced results, but also on their timing. Such systems are called real-time systems. Methods for system-level performance analysis play an integral part during the early design phase of embedded real-time systems. They support the analysis of various non-functional performance characteristics, and alleviate the choice of important design decisions before much time and resources are invested in detailed implementations. Compositional formal methods for performance analysis are able to quickly provide hard upper and lower bounds on performance characteristics. However, such analytical methods are limited in their scope and accuracy as they cannot incorporate many system details in the analysis. Interface-based design has been proposed in order to unify the steps of designing a system and analyzing it. It supports the paradigm for correct-by-construction design in the domain of embedded realtime systems. It can significantly shorten the design time of complex distributed embedded real-time systems. Recently, a method for Modular Performance Analysis based on Real-Time Calculus has been proposed that is also connected with the principles of interface-based design in the framework of Real-Time Interfaces. Both of them support the analysis and design of complex distributed embedded real-time systems. This thesis builds on these results and extends them in several directions. The main contributions of this work are summarized as follows: • A novel framework for interface-based design of distributed embedded real-time systems is proposed. It includes properties such as incremental design, independent-implementability, and refinement. It unifies many existing compositional performance analysis and interface-based design methods. • Novel models and methods for interface-based design are proposed that support the analysis and design of distributed embedded real-time systems which have buffer overflow and underflow constraints, end-to-end delay constraints, variable execution demands of tasks, and complex resource sharing policies. • A novel method for compositional performance analysis of marked graphs is proposed that can be used for distributed embedded real-time systems with cyclic data dependencies, finite buffers with blocking write semantics, variable execution demands of tasks, nondeterministic event streams and resource behaviors, and complex resource sharing policies. • A novel method for mode change performance analysis of multimode embedded real-time systems is proposed that can be used for systems with non-deterministic event streams and resource behaviors, variable execution demands of tasks, complex resource sharing policies, and various mode change protocols. • A novel scheduling server based on time division multiple access is proposed that can be reconfigured during run-time, and can guarantee the real-time properties of applications during reconfigurations.