Evolution Analysis of Large-Scale Software Systems Using Design Structure Matrices and Design Rule Theory

Designers often seek modular architectures to better accommodate expected changes and to enable parallel development. However, we lack a formal theory and model of modularity and software evolution, which can be used for description, prediction, and prescription. According to Baldwin and Clark's theory, modular architectures add value to system designs by creating options to improve the system by substituting or experimenting on individual modules. In this paper, we evaluate their theory by looking at the design evolution of two software product platforms through the modeling lens of design structure matrices (DSMs) and design rule theory. Our analysis shows that DSM models and options theory can explain how real-world modularization activities in one case allowed for different rates of evolution in different software modules and in another case conferred distinct strategic advantages on a firm (by permitting substitution of an at-risk software module without substantial change to the rest of the system). The experiment supports our hypothesis that these formal models and theory can account for important aspects of software design evolution in large-scale systems