Foreword to the Special Issue on Configurable Systems

Welcome to this special issue that includes empirical studies on configurable systems. This special issue in the Empirical Software Engineering journal is intended to provide the systems and software product lines community with a valuable collection of high-quality research articles that explore configurable systems with empirical studies. Particular attention was paid to research and industrial work carrying out experiments on configuration steps in the life cycle of system and software product lines. A configurable system is an artifact composed from instances of a set of predefined component types that can be composed and parameterized. The configuration step requires knowledge representation formalisms to capture variety and complexity of configurable products, but also acquisition methods and efficient reasoning algorithms for supporting solution search, to represent, and integrate user settings, personalization, and optimization. The configuration ends with the deployment and launches execution steps. This configuration can also change over time, because of a change of context. This is called reconfiguration. The majority of articles extend research presented at SPLC, the 23rd International Systems and Software Product Lines Conference. The conference was held from September 9 to 13, 2019 in Paris, France [1]. We received seventeen articles for this special issue. The call was open, but the SPLC 2019 authors were encouraged to prepare a revised and substantially extended version, and to consider as possible extensions additional practical applications determined by case studies or experiences, empirical validations, systematic comparisons with other approaches, or sound theoretical foundations. The submitted manuscripts were each peer reviewed by three reviewers. Finally, ten papers were accepted for inclusion in this special issue and six of them were extended versions of the SPLC 2019 research papers.