Much current research in computer science is concerned with two questions: is a program correct? And how can we improve a correct program preserving correctness? This latter question is known as the refinement of programs and the purpose of this book is to consider these questions in a formal setting. In fact, correctness turns out to be a special case of refinement and so the focus is on refinement. Although a reasonable background knowledge is assumed from mathematics and CS, the book is a self-contained introduction suitable for graduate students and researchers coming to this subject for the first time. There are numerous exercises provided of varying degrees of challenge.

Inhalt
1 Introduction.- 1.1 Contracts.- 1.2 Using Contracts.- 1.3 Computers as Agents.- 1.4 Algebra of Contracts.- 1.5 Programming Constructs.- 1.6 Specification Constructs.- 1.7 Correctness.- 1.8 Refinement of Programs.- 1.9 Background.- 1.10 Overview of the Book.- I Foundations.- 2 Posets, Lattices, and Categories.- 3 Higher-Order Logic.- 4 Functions.- 5 States and State Transformers.- 6 Truth Values.- 7 Predicates and Sets.- 8 Boolean Expressions and Conditionals.- 9 Relations.- 10 Types and Data Structures.- II Statements.- 11 Predicate Transformers.- 12 The Refinement Calculus Hierarchy.- 13 Statements.- 14 Statements as Games.- 15 Choice Semantics.- 16 Subclasses of Statements.- 17 Correctness and Refinement of Statements.- III Recursion and Iteration.- 18 Well-founded Sets and Ordinals.- 19 Fixed Points.- 20 Recursion.- 21 Iteration and Loops.- 22 Continuity and Executable Statements.- 23 Working with Arrays.- 24 The N-Queens Problem.- 25 Loops and Two-Person Games.- IV Statement Subclasses.- 26 Statement Classes and Normal Forms.- 27 Specification Statements.- 28 Refinement in Context.- 29 Iteration of Conjunctive Statements.- References.