Establishing the Correlation between Complexity and a Reliability Metric for Software Digital I&C-Systems

Faults introduced in design or during implementation might be prevented by design validation and by evaluation during implementation. There are numerous methods available for validating and evaluating software. Expert judgment is a much used approach to identify problematic areas in design or target challenges related to implementation. ISTec and IFE cooperate on a project on automated complexity measurements of software of digital instrumentation and control (I&C) systems. Metrics measured from the function blocks and logic diagrams specifying I&C-systems are used as input to a Bayesian Belief Net describing correlation between inputs and a complexity metric. By applying expert judgment in the algorithms for the automatic complexity evaluation, expert judgment is applied to entire software systems. The results from this approach can be used to identify parts of software which from a complexity viewpoint is eligible for closer inspection. In this paper we describe the approach in detail as well as plans for testing the approach.