Engineering of modern complex real time systems is driven by a host of design objectives, often differing not only in nature, importance, and form, but also in dimensional units and range, and themselves interacting in complex ways. These objectives influence design decisions throughout the entire system life cycle. We consider the problem of formulating the cost of a design decision driven by multiple objectives. We start by discussing issues and relationships among non functional objectives, their decomposition, and attribute cost functions used to quantify them. We then describe a hierarchical model along with an equational form for system cost function synthesis. Finally, examples are given to show how the model applies to actual multi objective problems in the design of complex real time systems.

In the design process of distributed real-time systems, a way must be found to cope with the complexity inherent in these systems. An established technique for this purpose is the decomposition of the system into smaller subsystems with well-defined, stable interfaces among them. In this paper, we propose a design method for the development of distributed real-time systems that are intended for safety-critical applications. The method is devised for the Time-Triggered Architecture, which constitutes such a real-time system. For the purpose of decomposition, we introduce a special type of interface, the so-called temporal firewall. In the Time-Triggered Architecture, there are three interfaces of this type-the Communication Network Interface, the Controlled Object Interface and the Gateway Interface-which partition the real-time system into autonomous subsystems. The design method clearly separates system and subsystem issues and focuses on the definition of the three interfaces between the subsystems. The feasibility and relevance of our design method is demonstrated by means of a small example from the automotive industry.

Analytically derived worst case execution time (WCET) bounds are prone to errors, because they often rely on information provided by the user. The paper presents a method for testing the results of static WCET analysis. The proposed test method is a blackbox test method that uses a genetic algorithm (GA) for test case generation. Important properties of the method are: (a) that it requires minimal information about possible impact data from the user and (b) that the GA guides data generation into directions that have a good chance to yield the real WCET of the program under test. Experimental results show that GA based testing produces results of high quality.

The time-triggered (TT) architecture approach supports the spatial partitioning of a large, distributed real-time system into a set of autonomous subsystems with small control-free data-sharing interfaces between them. This paper presents such a TT architecture and gives a detailed description of the interface between an autonomous time-triggered communication subsystem based on the TTP protocol and the host computer within a node of this architecture. This interface acts as a temporal firewall that eliminates the possibility of control error propagation from one subsystem to another subsystem. It thus facilitates the independent development and validation of the subsystems and supports the composability of the distributed architecture with respect to timeliness, validation, and certification.