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Abstract. Despite the undisputed prominence of inheritance as the fundamental reuse mechanism in object-oriented programming languages, the main variantssingle inheritance, multiple inheritance, and mixin inheritance -all suffer from conceptual and practical problems. In the first part of this paper, we identify and illustrate these problems. We then present traits, a simple compositional model for structuring object-oriented programs. A trait is essentially a group of pure methods that serves as a building block for classes and is a primitive unit of code reuse. In this model, classes are composed from a set of traits by specifying glue code that connects the traits together and accesses the necessary state. We demonstrate how traits overcome the problems arising from the different variants of inheritance, we discuss how traits can be implemented effectively, and we summarize our experience applying traits to refactor an existing class hierarchy.

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Reverse engineering software systems has become a major concern in software industry because of their sheer size and complexity. This problem needs to be tackled since the systems in question are of considerable worth to their owners and maintainers. In this article, we present the concept of a polymetric view, a lightweight software visualization technique enriched with software metrics information. Polymetric views help to understand the structure and detect problems of a software system in the initial phases of a reverse engineering process. We discuss the benefits and limits of several predefined polymetric views we have implemented in our tool CodeCrawler. Moreover, based on clusters of different polymetric views, we have developed a methodology which supports and guides a software engineer in the first phases of a reverse engineering of a large software system. We have refined this methodology by repeatedly applying it on industrial systems and illustrate it by applying a selection of polymetric views to a case study.

Abstract-To maintain and understand large applications, it is important to know their architecture. The first problem is that unlike classes and packages, architecture is not explicitly represented in the code. The second problem is that successful applications evolve over time, so their architecture inevitably drifts. Reconstructing the architecture and checking whether it is still valid is therefore an important aid. While there is a plethora of approaches and techniques supporting architecture reconstruction, there is no comprehensive software architecture reconstruction state of the art and it is often difficult to compare the approaches. This article presents a state of the art in software architecture reconstruction approaches.