Elegant Object-oriented Software Design via Interactive, Evolutionary Computation

TL;DR

This paper explores the role of elegance and symmetry in object-oriented software design by proposing new measures and demonstrating their correlation with subjective designer preferences through interactive evolutionary computation.

Contribution

It introduces four novel elegance measures based on distribution evenness and shows their significance in evolving elegant software designs.

Findings

Three elegance measures significantly correlate with designer preferences

Symmetry in class attributes and methods influences perceived elegance

Interactive evolution can effectively produce elegant software designs

Abstract

Design is fundamental to software development but can be demanding to perform. Thus to assist the software designer, evolutionary computing is being increasingly applied using machine-based, quantitative fitness functions to evolve software designs. However, in nature, elegance and symmetry play a crucial role in the reproductive fitness of various organisms. In addition, subjective evaluation has also been exploited in Interactive Evolutionary Computation (IEC). Therefore to investigate the role of elegance and symmetry in software design, four novel elegance measures are proposed based on the evenness of distribution of design elements. In controlled experiments in a dynamic interactive evolutionary computation environment, designers are presented with visualizations of object-oriented software designs, which they rank according to a subjective assessment of elegance. For three out of the four elegance measures proposed, it is found that a significant correlation exists between elegance values and reward elicited. These three elegance measures assess the evenness of distribution of (a) attributes and methods among classes, (b) external couples between classes, and (c) the ratio of attributes to methods. It is concluded that symmetrical elegance is in some way significant in software design, and that this can be exploited in dynamic, multi-objective interactive evolutionary computation to produce elegant software designs.