Can we avoid high coupling?

  • Authors:

  • Craig Taube-Schock;Robert J. Walker;Ian H. Witten

  • Affiliations:

  • University of Waikato, Hamilton, New Zealand;University of Calgary, Calgary, Canada;University of Waikato, Hamilton, New Zealand

  • Venue:
  • Proceedings of the 25th European conference on Object-oriented programming
  • Year:
  • 2011

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Abstract

It is considered good software design practice to organize source code into modules and to favour within-module connections (cohesion) over between-module connections (coupling), leading to the oft-repeated maxim "low coupling/high cohesion". Prior research into network theory and its application to software systems has found evidence that many important properties in real software systems exhibit approximately scale-free structure, including coupling; researchers have claimed that such scale-free structures are ubiquitous. This implies that high coupling must be unavoidable, statistically speaking, apparently contradicting standard ideas about software structure. We present a model that leads to the simple predictions that approximately scale-free structures ought to arise both for between-module connectivity and overall connectivity, and not as the result of poor design or optimization shortcuts. These predictions are borne out by our large-scale empirical study. Hence we conclude that high coupling is not avoidable--and that this is in fact quite reasonable.