Dynamic Logic for Java

Abstract

In this chapter, we introduce an instance of dynamic logic, called JavaDL, that allows us to reason about Java programs. Dynamic logic extends first-order logic and makes it possible to consider several program states in a single formula. Its principle is the formulation of assertions about program behavior by integrating programs and formulas within a single language. We present a sequent calculus for JavaDL, which is used in the KeY System for verifying Java programs. Deduction in this calculus is based on symbolic program execution and simple program transformations and is, thus, close to a programmer's understanding of Java. Besides rules for symbolic execution, the calculus contains rules for program abstraction and modularization, including invariant rules for reasoning about loops and rules that replace a method invocation by the method's contract.