S.S. Gokhale (USA)
Software structure, Software reliability
Software reliability growth models (SRGMs) are inade quate to assess the reliability of modern, heterogeneous, componentbased software systems since these models treat the system as a black box and model its input/output behavior without looking into its internal structure. De velopment of techniques to assess the reliability of a componentbased software system (which may be assem bled from a variety of components, some picked offthe shelf, some developed inhouse and some developed con tractually), based on its structure is thus absolutely essen tial. Most of the prior efforts in the area of structurebased reliability assessment use the composite solution approach to predict the expected reliability of the system. While the composite approach produces an accurate reliability esti mate, it does not explicitly relate system reliability to the reliabilities of the individual components and system struc ture. The hierarchical approach, on the other hand, pro duces a mathematical expression relating the system reli ability to the reliability of its individual components and system structure. Such an expression facilitates sensitiv ity analysis, exploration of alternatives through optimiza tion and identification of reliability bottlenecks. However, the reliability estimate obtained using the hierarchical ap proach is only an approximation of the one obtained using the composite approach. In this paper we develop an ac curate hierarchical method to estimate the reliability of a software system based on its structure. The method incor porates secondorder structural statistics, and hence pro vides an estimate that is closer to the one produced by the composite approach. Due to the improved accuracy in the reliability estimate afforded by our method, the hierarchi cal approach may be used with greater confidence for other purposes. We illustrate the use of our method with a case study.
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