Software Reuse and Reusability Based on Requirements: Product Lines, Cases and Feature-Similarity Models

Several socioeconomic trends are increasing personalised customer demands. Suppliers are responding with mass customisation but the management of large-scale cost-effective software reuse remains a difficult challenge. Software reuse and reusability range from operational, ad-hoc and short-term to strategic, planned and long-term. Often the focus of attention is just on code or low-level design. This tutorial presents and compares two different requirements-led approaches. The first approach deals with requirements reuse and reusability in the context of product line engineering. The second approach deals with requirements reuse and reusability in the context of case-based reasoning. Both approaches have different key properties and trade-offs between the costs of making software artefacts reusable and the benefits of reusing them. To aid large-scale development we have proposed a Feature-Similarity Model, which draws on both approaches to facilitate discovering requirements relationships using similarity metrics. A Feature-Similarity Model also helps with the evolution of a product line, since new requirements can be introduced first into a case base and then gradually included into a product line representation.