 Rather than put general software components into a library in the hope that opportunities for reuse will arise, software product lines only call for software artifacts to be created when reuse is predicted in one or more products in a well defined product line.Recent advances in the software product line field have demonstrated that narrow and strategic application of these concepts can yield order of magnitude improvements in software engineering capability.The result is often a discontinuous jump in competitive business advantage, similar to that seen when manufacturers adopt mass production and mass customization paradigms.