Software product lines: what to do when enumeration won't work

The history of research on the development of program-families is briefly reviewed. Two distinct problems, configuration-management and family-design are identified. It is explained that, while software configuration-management is not fundamentally different from configurationmanagement for other products, in practice, inadequate attention to family-design exacerbates all problems associated with developing and maintaining program families. It is suggested that although enumeration is useable for configuration-management, product-line design by enumeration is not generally feasible. An alternative approach, family member characterization using abstract documentation, is discussed. This approach is practical for family-design and can make configuration-management easier. The advantages of designing an interface in terms of programs over an interface expressed as a data structure using conventions such as XML are also discussed.