Johan Fredriksson

The SAVE approach to component-based development of vehicular systems

The component-based strategy aims at managing complexity, shortening time-to-market, and reducing maintenance requirements by building systems with existing components. The full potential of this strategy has not yet been demonstrated for embedded software, mainly because of specific requirements in the domain, e.g., those related to timing, dependability, and resource consumption. We present SaveCCT - a component technology intended for vehicular systems, show the applicability of SaveCCT in the engineering process, and demonstrate its suitability for vehicular systems in an industrial case-study. Our experiments indicate that SaveCCT provides appropriate expressiveness, resource efficiency, analysis and verification support for component-based development of vehicular software.

Evaluation of component technologies with respect to industrial requirements

We compare existing component technologies for embedded systems with respect to industrial requirements. The requirements are collected from the vehicular industry, but our findings are applicable to similar industries developing resource constrained safety critical embedded distributed real-time computer systems. One of our conclusions is that none of the studied technologies is a perfect match for the industrial requirements. Furthermore, no single technology stands out as being a significantly better choice than the others; each technology has its own pros and cons. The results of our evaluation can be used to guide modifications or extensions to existing technologies, making them better suited for industrial deployment. Companies that want to make use of component-based software engineering as available today can use this evaluation to select a suitable technology.

Introducing a Component Technology for Safety Critical Embedded Real-Time Systems

Safety critical embedded real-time systems represent a class of systems that has attracted relatively little attention in research addressing component based software engineering. Hence, the most widely spread component technologies are not used for resource constrained safety critical real-time systems. They are simply to resource demanding, to complex and to unpredictable. In this paper we show how to use component based software engineering for low footprint systems with very high demands on safe and reliable behaviour. The key concept is to provide expressive design time models and yet resource effective run-time models by statically resolve resource usage and timing by powerful compile time techniques. This results in a component technology for resource effective and temporally verified mapping of a component model to a commercial real-time operating system.

Contract-Based ReusableWorst-Case Execution Time Estimate

We present a contract-based technique to achieve reuse of known worst-case execution times (WCET) in conjunction with reuse of software components. For resource constrained systems, or systems where high degree of predictability is needed, classical techniques for WCET- estimation will result in unacceptable overestimation of the execution-time of reusable software components with rich behavior. Our technique allows different WCETs to be associated with subsets of the component behavior. The appropriate WCET for any usage context of the component is selected be means of component contracts over the input domain. In a case-study we illustrate our technique and demonstrate its potential in achieving tight WCET- estimates for reusable components with rich behavior.

Optimizing resource usage in component-based real-time systems

The embedded systems domain represents a class of systems that have high requirements on cost efficiency as well as run-time properties such as timeliness and dependability. The research on component-based systems has produced component technologies for guaranteeing real-time properties. However, the issue of saving resources by allocating several components to real-time tasks has gained little focus. Trade-offs when allocating components to tasks are, e.g., CPU-overhead, footprint and integrity. In this paper we present a general approach for allocating components to real-time tasks, while utilizing existing real-time analysis to ensure a feasible allocation. We demonstrate that CPU-overhead and memory consumption can be reduced by as much as 48% and 32% respectively for industrially representative systems.

Reusable Component Analysis for Component-Based Embedded Real-Time Systems

Component-Based Software Engineering (CBSE) promises an improved ability to reuse software which would potentially decrease the development time while also improving the quality of the system, since the components are (re-)used by many. However, CBSE has not been as successful in the embedded systems domain as in the desktop domain, partly because requirements on embedded systems are stricter (e.g. requirements on safety, real-time and minimizing hardware resources). Moreover these requirements differ between industrial domains. Paradoxically, components should be context-unaware to be reusable at the same time as they should be context sensitive in order to be predictable and resource efficient. This seems to be a fundamental problem to overcome before the CBSE paradigm will be successful also in the embedded systems domain. Another problem is that some of the stricter requirements for embedded systems require certain analyses to be made, which may be very complicated and time-consuming for the system developer. This paper describes how one particular kind of analysis, of worst-case execution time, would fit into the CBSE development processes so that the component developer performs some analyses and presents the results in a form that is easily used for component and system verification during system development. This process model is not restricted to worst-case execution time analysis, but we believe other types of analyses could be performed in a similar way.

Application of built-in-testing in component-based embedded systems

This work-in-progress paper discusses challenges with application of Built-In Testing (BIT) in component-based embedded-systems. Testing constitutes a large part of the time and budget in development of embedded software systems. Such systems are often mission-critical, making testing highly important, and at the same time testing embedded systems is challenging because of their limited observability. We investigate the possible application of BIT in components for embedded systems, as a technique to advance the technology and knowledge for analysis and verification of functional correctness, real-time behavior, safety, and reliability of these systems.

Deriving the Worst-Case Execution Time Input Values

Worst-Case Execution Time (WCET) analysis derives upper bounds for execution times of programs. Such bounds are crucial when designing and verifying real-time systems. A major problem with today’s WCET analysis approaches is that there is no feedback on the particular values of the input variables that cause the program’s WCET. However, this is important information for the real-time system developer.We present a novel approach to overcome this problem. In particular, we present a method, based on a combination of input sensitive static WCET analysis and systematic search over the value space of the input variables, to derive the input value combination that causes the WCET. We also present several different approaches to speed up the search. Our evaluations show that the WCET input values can be relatively quickly derived for many type of programs, even for program with large input value spaces. We also show that the WCET estimates derived using the WCET input values often are much tighter than the WCET estimates derived when all possible input value combinations are taken into account.

A component-based development framework for supporting functional and non-functional analysis in control system design

The use of component-based development (CBD) is growing in the software engineering community and it has been successfully applied in many engineering domains such as office applications and in web-based distributed applications. Recently, the need of CBD is growing also in other domains related to dependable and embedded systems, namely, in the control engineering domain. However, the widely used commercial component technologies are unable to provide solutions to the requirements of embedded systems as they require too much resources and they do not provide methods and tools for developing predictable and analyzable embedded systems. There is a need for new component-based technologies appropriate to development of embedded systems. In this paper we briefly present a component-based development framework called SAVEComp. SAVEComp is developed for safety-critical real-time systems. One of the main characteristics of SAVEComp is syntactic and semantic simplicity which enables a high analyzability of properties important for embedded systems. We discuss how SAVEComp is able to provide an efficient support for designing and implementing embedded control systems by mainly focusing on simplicity and analyzability of functional requirements and of real-time and dependability quality attributes. In particular we discuss the typical solutions of control systems in which feedback loops are used and which significantly complicate the design process. We provide a solution for increasing design abstraction level and still being able to reason about system properties using SAVEComp approach. Finally, we discuss an extension of SAVEComp with dynamic run-time property checking by utilizing run-time spare capacity that is normally induced by real-time analysis.