Software system reliability and safety assessment: an extended FMEA approach

Abstract

This paper presents a methodology for assessing the reliability and safety of a software based on an extended Failure Modes and Effects Analysis (FMEA) approach. The methodology is described in steps with illustrative examples. The analysis starts from initial phase of the software development and evolves during the subsequent phases of software development providing valuable information to each phases. Finally, the analysis yields a quantitative assessment of reliability and safety of the software system. The paper's main objective is to support Probabilistic Safety Assessment (PSA) in assessing risk. Risk is a function of severity and failure frequency/probability. The severity is characteristic of failure effects. Failures may be analysed as functional or component failure. In this paper, it is proposed to consider severity levels at functional failure level as it is easier to understand failure effects at functional level. Moreover, various logical combinations of different functional failures can also be formed and analysed using the proposed approach.