Software Complexity: Toward a Unified Theory of Coupling and Cohesion

Knowledge work is generally regarded as involving complex cognition, and few types of knowledge work are as important in the modern economy as software engineering (SE). A large number of measures have been developed to analyze software and its concomitant processes with the goals of evaluating, predicting and controlling its complexity. While many effective measures can be used to achieve these goals, there is no firm theoretical basis for choosing among measures. The first research question for this paper is: how to theoretically determine a parsimonious subset of software measures to use in software complexity analysis? To answer this question, task complexity is studied; specifically Wood’s model of task complexity is examined for relevant insights. The result is that coupling and cohesion stand out as comprising one such parsimonious subset. The second research question asks: how to resolve potential conflicts between coupling and cohesion? Analysis of the information processing view of cognition results in a model of cohesion as a moderator on a main relationship between coupling and complexity. The theory-driven approach taken in this research considers both the task complexity model and cognition and lends significant support to the developed model for software complexity. Furthermore, examination of the task complexity model steers this paper towards considering complexity in the holistic sense of an entire program, rather than of a single program unit, as is conventionally done. Finally, it is intended that by focusing software measurement on coupling and cohesion, research can more fruitfully aid both the practice and pedagogy of software complexity management.