Typical object-oriented (OO) systems implement several functional features that are interwoven into class hierarchies. In the absence of aspect-oriented techniques to develop and compose these features, developers resort to object-oriented design and programming idioms to separate features as well as possible. Given a legacy OO system, discovering existing functional features helps understand the design of the system and extract these features to ease their maintenance and reuse. We want to discover candidate functional features in OO systems. We first define functional features and then discuss the footprints that such features are likely to leave in an OO system. We identify three such footprints: (1) multiple inheritance, (2) delegation, and (3) ad-hoc. We develop a set of algorithms for identifying such footprints in OO code and implemented them for the Java language using Eclipse JDT. In this article, we present the algorithms, and the results of applying the corresponding tools on five open-source systems: FreeMind, JavaWebMail, JHotDraw, JReversePro, and Lucene. Our experimental results show that: (1) the different algorithms can identify interesting and useful candidate functional features in OO systems, (2) they can identify opportunities for refactoring, and (3) they are complementary and could help developers.

Legacy OO applications typically implement a number of functional features. In the absence of aspect-oriented development techniques to separately develop and maintain these features, they end up embodied in the same class hierarchies. That embodiement depends on the design technique used to implement them. We identified three such design techniques: a) multiple inheritance– or simulations thereof, b) delegation, and c) what we referred to as adhoc implementation. We are interested in developing techniques for identifying and isolating code fragments that implement distinct functional features. Here, we explore the use of concept analysis to detect ad-hoc implementations of features. We present the principles underlying our overall approach, a concrete method for identifying functional features in legacy code, and the results of preliminary experimentation.

Aspect-oriented software development builds upon object-oriented (OO) development by offering additional abstraction boundaries that help us separate different types of requirements into so-called aspects. Given a legacy OO application, it pays to identify existing aspects to help understand the structure of the application and potentially to extract those aspects into separate software modules that can be maintained and reused individually. We are interested in the extraction and repackaging of functional aspects. We first characterize what we mean by functional aspect, and then explore the properties that such aspects are likely to exhibit in a legacy application that integrate such aspects. Next, we present algorithms for extracting such aspects, and the preliminary results we obtained. We conclude by discussing directions for future research.