This volume is dedicated to the memory of Paulo A. S. Veloso (1944-2020), a distinguished Brazilian logician. Veloso's scientific contributions are disseminated in the most important areas related to logic: computer science, mathematics and philosophy. His main contributions are in the fields of automata theory, algebraic logic, formal specifications, modal logics, and diagrammatic reasoning. In addition to his intellectual depth and innovative ideas, Veloso was known for his kindness and generosity, both academic and personal, attested by the large number of collaborators and friends he cultivated throughout his career. It was high time some of these collaborators and friends worked together. The result is this book, which contains brilliant contributions in the various subjects directly related to Paulo Veloso's outstanding work.