On the notion of variability in software product lines

The authors discuss the notion of variability. We have experienced that this concept has so far been underdefined, although we have observed that variability techniques become increasingly important. A clear indication of this trend is the recent emergence of software product lines. Software product lines are large, industrial software systems intended to specialize into specific software products. The authors provide a framework of terminology and concepts regarding variability. In addition, they present three recurring patterns of variability. Finally, they suggest a method for managing variability in software product lines.