Expressing Design by Contract Principles using Aspects

This thesis deals with two methodologies in software construction: Aspect Oriented Programming and Design by Contract. It was already claimed that the design by contract methodology is an aspect of the software system. As such, a contract can be expressed in AOP terminology, and hence could be enforced using an aspect oriented based tool. The work presented here describes the enforcement process, and divides it into the building blocks of design by contract. For each building block we present a constructive way to express its essence in AspectJ, an aspect oriented programming language . The devil lies in the details. There are several issues as precondition subcontracting, collecting old values and others that needed some research effort in both AOP and DbC fields. The research yielded a discussion about AspectJ semantics on the one hand and variants of design by contract on the other. On the AOP part this work investigates the semantics of call and execution pointcuts in AspectJ, and their interaction with inheritance. On the DbC part this work presents some variants and extensions to original design by contract introduced by Meyer, namely contract enforcement with respect to the client, class oriented contract (static assertions), enforcement of reflexive contracts and others.