As a result of the technological progress, software development environment has changed into development paradigm based on client/server systems by using network computing technologies. Network technologies have made rapid progress with the dissemination of computer systems in all areas. These network technologies become increasingly more complex in a wide sphere. Especially, open source software systems which serve as key components of critical infrastructures in the society are still ever-expanding now. In this paper, we propose a method of software reliability assessment based on stochastic differential equations. Especially, we derive several assessment measures in terms of imperfect debugging. Also, we analyze actual software fault-count data to show numerical examples of software reliability assessment for an embedded open source software. Further, it has been necessary to manage the software development process in terms of reliability, effort, and release time. Then, we find the optimal release time based on the total expected software maintenance effort.
An NHPP Software Reliability Model with S-Shaped Growth Curve Subject to Random Operating Environments and Optimal Release Time