This Festschrift, dedicated to Manuel Hermenegildo on the occasion of his 60th birthday, contains papers written by many of his closest collaborators. Manuel received his Ph.D. degree in Computer Science and Engineering from the University of Texas at Austin, and among various positions he was an endowed chair in Information Science and Technology at the University of New Mexico. In 2007 he became the founding director of the IMDEA Software Institute, where he is now a Distinguished Professor, while also a full professor at Universidad Politécnica de Madrid (UPM).He has published more than 300 scientific publications, given numerous keynotes and invited talks at major conferences, coordinated many national and international projects, and served the community in major conference roles, on journal boards, and on funding, scientific, and research committees. Among his awards are the Julio Rey Pastor prize in Mathematics and Information Science and Technology and the Aritmel prize in Computer Science; he is an elected member of the Academia Europaea; and in 2022 he was elected a Fellow of the ACM for contributions to program analysis, verification, parallelism, logic programming, and the IMDEA Software Institute. Throughout his career Manuel has shown his amazing capacity for detailed work, thoroughness, and expert contributions, along with the interpersonal skills needed for successful collaboration, such as a positive attitude and a sense of humor. The contributions in this volume reflect the quality and the scope of his research interests and mentoring successes.

This book constitutes the thoroughly refereed post-conference proceedings of the 26th International Symposium on Logic-Based Program Synthesis and Transformation, LOPSTR 2016, held in Edinburgh, UK, in September 2016. The 20 revised full papers presented together with the abstracts of 3 invited talks were carefully reviewed and selected from 38 submissions. The aim of the LOPSTR series is to stimulate and promote international research and collaboration on logic-based program development. LOPSTR is open to contributions in all aspects of logic-based program development, all stages of the software life cycle, and issues of both programming-in-the-small and programming-in-the-large. LOPSTR traditionally solicits contributions, in any language paradigm, in the areas of synthesis, specification, transformation, analysis and verification, specialization, testing and certification, composition, program/model manipulation, optimization, transformational techniques in SE, inversion, applications, and tools.