Transformations everywhere

This special issue is devoted to “program transformation” in the sense of tool-supported adaptation of software systems. Software engineering and software re-engineering rely on such transformations, which are automated in, for example, tools for refactoring, migration, program specialisation, compiler optimisation, database re-engineering, software configuration, business-rule extraction, aspect weaving, aspect mining, architectural modifications, and model-driven approaches. This special issue bundles ten state-of-the-art contributions, while covering the broad area of program transformation in a complementary, almost survey-like manner. Three papers relate to refactoring—to the composition problem, to reasoning about correctness, and to the details of challenging refactoring samples. Two papers survey successful transformation systems, namely the Tempo system for program specialisation, and the FermaT system for software migration. One paper develops concepts for run-time system transformations. Finally, four papers communicate idioms or concepts for transformation systems: higher-order and dynamic traversals, the use of flow analysis for driving transformations, validated compiler transformations, and the cause–effect patterns in partial evaluation. This introduction to the special issue briefly describes the articles included, and connects them to general concerns in research on program transformation. In addition, a list of research challenges is compiled, which will perhaps be useful in the further exploration of the area of program transformation.