This book includes formal definitions and properties of semiring-based soft constraints, as well as their use within constraint logic programming and concurrent constraint programming. Moreover, the author shows how to adapt existing notions and techniques such as abstraction and interchangeability to the soft constraint framework and it is demonstrated how soft constraints can be used in some application areas, such as security. Overall, this book is a great starting point for anyone interested in understanding the basics of semiring-based soft constraints.