Architectural Complexity of Large-Scale Software Systems

Today companies apply software systems with more than 14 million Lines of Code (LOC), which are still maintainable and expandable in spite of their size. On the other hand, you will find smaller software systems (> 200,000 LOC), which can either only be adapted with considerable effort, or which cannot be adapted at all. Why are some software systems fraught with maintenance problems while others remain manageable? Based on twenty-four industrial case studies on object-oriented Java projects, this paper identifies aspects of architectural complexity and describes which route should be taken to keep the architectural complexity of large-scale software systems controllable. In this context it becomes clear that in every case the architectural style is pivotal in determining whether the software system will be maintainable over a longer period and thus prevent software erosion.