The text first presents a framework for the formulation of language models, focusing on equational calculi and abstract machines, and then introduces PLT Redex, a suite of software tools for expressing these models as PLT Redex models.

PLT Redex comes with the PLT Scheme implementation, available free at http://www.plt-scheme.org/. Readers can download the software and experiment with Redex as they work their way through the book.

This book is useful for the working semantics engineer (graduate student or professional language designer).

“Courses on semantics can easily become as dry as dust; in contrast, this book is nothing short of revolutionary. The first part is a very clear explanation of the basic concepts in programming language semantics, starting with abstract models and moving to progressively more concrete ones. However, the book really comes alive in the second part, where the authors use the PLT Redex language that they have developed to interactively explore language semantics in the same way that DrScheme allows the interactive exploration of programs. I believe that this approach will become the standards way of doing semantics research in the future, and there is no better way to take advantage of it than to read this book.”