Which Software Modules have Faults which will be Discovered by Customers?

Abstract

Software is the medium for implementing increasingly sophisticated features during the maintenance phase as successive releases are developed. Software quality models can predict which software modules are likely to have faults that will be discovered by customers. Such models are key components of a system such as Enhanced Measurement for Early Risk Assessment of Latent Defects (EMERALD). It is a sophisticated system of decision support tools used by software designers and managers at Nortel to assess risk and improve software quality and reliability of legacy software systems. This paper reports an approach to software quality modelling that is suitable for industrial systems such as EMERALD. We conducted a case study of a large legacy telecommunications system in the maintenance phase to predict whether each module will be considered fault‐prone. The case study is distinctive in the following respects. (1) Fault‐prone modules were defined in terms of faults discovered by customers, which represent only a small fraction of the modules in the system. (2) We developed models based on software product and process metrics that can make useful predictions at the end of the coding phase and at the time of release. (3) The modelling approach is suitable for very large systems. We anticipate that refinements of this case study's models will be incorporated into EMERALD. A similar approach could be taken for other systems. Copyright © 1999 John Wiley & Sons, Ltd.