The subject of this book is modular approaches to the verification and control of discrete-event systems (DES). DES are dynamic systems characterized by discrete states and event-driven evolution. In recent years, a substantial body of work has been built up to provide a theory and framework for the control and verification of DES. Despite all the advancements that have been made in this area, application to real-life systems has been somewhat slow. A significant hurdle to the adoption of these methods is the state-space explosion that occurs in modeling systems of the size most commonly found in industry. This book develops three new modular approaches to the supervisory control of DES that reduce complexity through the use of abstraction and interfaces. The advantages and limitations of these approaches are presented in the context of the current state of the art through illustrative examples.