A Software Profiling Methodology for Design and Assessment of Dependable Software

Doktorsavhandling, 2002

The advent of computerized consumer products, such as for example automobiles, mobile systems, etc., has produced a large increase in the need for dependable (or robust) systems. As cost is a relevant issue for such systems, the cost of dependability has to be kept low. Furthermore, as the replication of software is virtually free compared to the replication of hardware, the trend is to implement more and more functions in software. This motivates the search for methodologies for cost efficient design and assessment of dependable software. An established approach for designing dependable software entails addition of error detection mechanisms (EDM's) and error recovery mechanisms (ERM's). The effectiveness of these mechanisms, however, is achieved only if their composition is matched with their placement in locations where they are actually effective. It is the development of a systematic methodology to profile software in order to compose and locate EDM's and ERM's, that this thesis endeavors to achieve. Presented in this thesis is a set of approaches for profiling software such that the most vulnerable and/or critical modules and signals can be identified in a quantifiable way. The profiling methodology relies on the analysis of error propagation and error effect in modular software. The results obtainable with these profiles indicate where in a given software system, errors tend to propagate and where they tend to cause the most damage as experienced by the environment. The main contribution of this thesis is a software profiling methodology that encompasses development of the fault injection tool suite PROPANE (Propagation Analysis Environment) and the analysis framework EPIC (Exposure, Permeability, Impact, Criticality---the four main metrics introduced in the framework). The vision is that this contribution can aid software developers in the design and assessment of dependable software in the early stages of development.