Gabriele Bavota, Andrea De Lucia, Andrian Marcus, Rocco Oliveto
During its lifecycle, the internal structure of a software system undergoes continuous modifications. These changes push away the source code from its original design, often reducing its quality. In such cases, refactoring techniques can be applied to improve the readability and reducing the complexity of source code, to improve the architecture and provide for better software extensibility. Despite its advantages, performing refactoring in large and nontrivial software systems might be very challenging. Thus, a lot of effort has been devoted to the definition of automatic or semi-automatic approaches to support developer during software refactoring. Many of the proposed techniques are for recommending refactoring operations. In this chapter, we present guidelines on how to build such recommendation systems and how to evaluate them. We also highlight some of the challenges that exist in the field, pointing toward future research directions.