An analysis of modularity in aspect oriented design

We present an analysis of modularity in aspect oriented design using the theory of modular design developed by Baldwin and Clark [10]. We use the three major elements of that theory, namely: i) Design Structure Matrix (DSM), an analysis and modeling tool; ii) Modular Operators, units of variations for design evolution; and iii) Net Options Value (NOV), a quantitative approach to evaluate design. We study the design evolution of a Web Services application where we observe the effects of applying aspect oriented modularization.Based on our analysis we get to the following three main conclusions. First, on the structural part, it is possible to apply the DSM to aspect oriented modularizations in a straightforward manner, i.e. without modifications to DSMs basic model. This shows that aspects can, in fact, be treated as modules of design. Second, the evolution of a design into including aspect modules uses the modular operators proposed by Baldwin and Clark, with a variant of the Inversion operator. This variant captures taking redundant, scattered information hidden in modules and moving it down or keeping it at the same level in the design hierarchy. Third, when calculating and comparing NOVs of the different designs of our application, we obtained higher NOV for the design with aspects than for the design without aspects. This shows that, under this theory of modularity, certain aspect oriented modularizations can add value to the design.