Scenario-based reliability analysis of component-based software

Sherif Yacoub, Bojan Cukic, and Hany Ammar Computer Science and Electrical Eng. Dept., West Virginia University, Morgantown, WV 26506-6109 {yacoub,cukic,ammar}@csee.wvu.edu Abstract Software designers are motivated to utilize off-the-shelf software components for rapid application development. Such applications are expected to have high reliability as a result of deploying trusted components. The claims of high reliability need further investigation based on reliability estimation models and techniques that are applicable to component-based applications. This paper introduces a probabilistic model and a reliability estimation and analysis technique applicable to high-level designs. The technique is named "Scenario-Based Reliability Estimation" (SBRE). SBRE is specific for component-based software whose analysis is strictly based on execution scenarios. Using scenarios, we construct a probabilistic model named "Component-Dependency Graph" (CDG). CDGs are directed graphs that represent components, component reliabilities, link and interface reliabilities, transitions, transition probabilities, and average execution times of components. In CDGs, component interfaces and link reliabilities are treated as first class element of the model. Based on CDGs, an algorithm is presented to analyze the reliability of the application as function of the reliability of its components and interfaces. A case study illustrates the applicability of the algorithm. The SBRE algorithm is used to identify critical components and critical component interfaces by investigating the sensitivity of the application reliability to changes in the reliabilities of components and their interfaces.