Maintaining feature traceability with embedded annotations

Features are commonly used to describe functional and nonfunctional aspects of software. To effectively evolve and reuse features, their location in software assets has to be known. However, locating features is often difficult given their crosscutting nature. Once implemented, the knowledge about a feature's location quickly deteriorates, requiring expensive recovering of these locations. Manually recording and maintaining traceability information is generally considered expensive and error-prone. In this paper, we argue to the contrary and hypothesize that such information can be effectively embedded into software assets, and that arising costs will be amortized by the benefits of this information later during development. We test this hypothesis in a study where we simulate the development of a product line of cloned/forked projects using a lightweight code annotation approach. We identify annotation evolution patterns and measure the cost and benefit of these annotations. Our results show that not only the cost of adding annotations, but also that of maintaining them is small compared to the actual development cost. Embedding the annotations into assets significantly reduced the maintenance cost because they naturally co-evolve with the assets. Our results also show that a majority of these annotations provides a benefit for feature-related code maintenance tasks, such as feature propagation and migrating clones into a platform.