Cees Pierik

A Syntax-Directed Hoare Logic for Object-Oriented Programming Concepts

This paper outlines a sound and complete Hoare logic for a sequential object-oriented language with inheritance and subtyping like Java. It describes a weakest precondition calculus for assignments and object-creation, as well as Hoare rules for reasoning about (mutually recursive) method invocations with dynamic binding. Our approach enables reasoning at an abstraction level that coincides with the general abstraction level of object-oriented languages.

Computer-aided specification and verification of annotated object-oriented programs

The main contribution of this paper consists of a description of a front-end tool which supports the computer-aided specification and verification of a class of flowcharts which capture the basic dynamics of object-oriented programs. The specific emphasis of our approach is on the automated verification of flowcharts annotated with assertions which allow one to specify properties directly in terms of the source code itself instead of some particular model of its semantics.

How to Cook a Complete Hoare Logic for Your Pet OO Language

This paper introduces a general methodology for obtaining complete Hoare logics for object-oriented languages. The methodology is based on a new completeness result of a Hoare logic for a procedural language with dynamically allocated variables. This new result involves a generalization of Gorelick’s seminal completeness result of the standard Hoare logic for recursive procedures with simple variables. We show how this completeness result can be generalized to existing Hoare logics for typical object-oriented concepts like method calls, sub-typing and inheritance, and dynamic binding, by transforming an encoding of these concepts into this procedural language with dynamically allocated variables.

Controlling object allocation using creation guards

Sharing of objects between different modules is often necessary to meet speed and resource demands. The invariants that describe properties of shared objects are difficult to maintain because they can be falsifiable by object allocation. This paper introduces creation guards to obtain a sound and modular methodology that supports such invariants.

Modularity and the Rule of Adaptation

This paper presents a new rule for reasoning about method calls in object-oriented programs. It is an adaptation of Hoare’s rule of adaptation to the object-oriented paradigm, which takes both the write effects and the creational effects of a method into account. The new rule contributes in various ways to the modularity of the specification. We also argue that our rule of adaptation is the missing link between Hoare logics and proof outlines for object-oriented programs.

Coordinating Agents in OO

In this paper we introduce an object-oriented coordination language for multi-agents systems. The beliefs and reasoning capabilities of an agent are specified in terms of a corresponding abstract data type. Agents interact via an extension of the usual object-oriented message passing mechanism. This extension provides the autonomy that is required of agents but which objects in most object-oriented languages do not have. It consists of an explicit answer statement by means of which an agent can specify that it is willing to accept some specified messages. For our coordination language we also present a formal method for proving correctness. The method extends and generalizes existing assertional proof methods for object-oriented languages.