By a specification language we understand a formal system of syntax, semantics and proof rules. The syntax and semantics define a language; the proof rules define a proof system. Specifications are expressions in the language, and reasoning over properties of these specifications is done within the proof system. This book presents comprehensive studies on nine specification languages and their logics of reasoning. The editors and authors are authorities on these specification languages and their application. Dedicated chapters address: the use of ASM (Abstract State Machines) in the classroom; the Event-B modelling method; a methodological guide to CafeOBJ logic; CASL, the Common Algebraic Specification Language; the Duration Calculus; the logic of the RAISE specification language (RSL); the specification language TLA+; the typed logic of partial functions and the Vienna Development Method (VDM); and Z logic and its applications. Each chapter is self-contained, with references, and symbol and concept indexes. Finally, in a unique feature, the book closes with short commentaries on the specification languages written by researchers closely associated with their original development. With extensive references and pointers to future developments, this book will be of interest to researchers and graduate students engaged with formal specification languages.