SOFTWARE-RELIABILITY TREND ANALYSES FROM THEORETICAL TO PRACTICAL CONSIDERATIONS

This concise paper addresses the problem of reliability growth charact erization and analysis. It is intended to show how reliability trend a nalyses can help the project manager in controlling the progress of th e development activities and in appreciating the efficiency of the tes t programs. Reliability trend change may result from various reasons, some of them are desirable and expected (such as reliability growth du e to fault removal) and some of them are undesirable (such as slowing down of the testing effectiveness). Identification in time of the latt er allows the project manager to take the appropriate decisions very q uickly in order to avoid problems which may manifest later. The notion s of reliability growth over a given interval and local reliability tr end change are introduced through the subadditive property, allowing b etter definition and understanding of the reliability growth phenomena ; the already existing trend tests are then revisited using these conc epts. Emphasis is put on the way trend tests can be used to help the m anagement of the testing and validation process and on practical resul ts that can be derived from their use; it is shown that, for several c ircumstances, trend analyses give information of prime importance to t he developer.