Continuous and discontinuous software evolution: aspects of software evolution across multiple product lines

This article discusses continuous and discontinuous evolutions across multiple products lines of software systems. As an empirical study, we analyzed the evolution of mobile phone software systems, which have undergone an extremely fast evolution from voice communication systems through mobile Internet terminals, to mobile Javaenabled terminals for the last four years. Along with the evolution, the software systems created three product lines and the size has quadrupled. This article discusses aspects of such extremely fast evolution and reveals continuity and discontinuity of software evolution. We claim that discontinuity is essential aspect of software evolution and taming discontinuous evolution is the challenge in the evolutionary development of software systems.