Process Modelling to Support Dependability Arguments

This paper reports work to support dependability arguments about the future reliability of a product before there is direct empirical evidence. We develop a method for estimating the number of residual faults at the time of release from a “barrier model” of the development process, where in each phase faults are created or detected. These estimates can be used in a conservative theory in which a reliability bound can be obtained or can be used to support arguments of fault freeness. We present the work done to demonstrate that the model can be applied in practice. A company that develops safety-critical systems provided access to two projects as well as data over a wide range of past projects. The software development process as enacted was determined and we developed a number of probabilistic process models calibrated with generic data from the literature and from the company projects. The predictive power of the various models was compared.

• Type: Conference
• Year: 2002
• Where: DSN
• Authors: Robin E. Bloomfield, Sofia Guerra
• Keywords: Computer Networks, Development Process, Direct Empirical Evidence, DSN 2002, Residual Faults