Modifications, Tweaks, and Bug Fixes in Architectural Tactics

Architectural qualities such as reliability, performance, and security, are often realized in a software system through the adoption of tactical design decisions such as the decision to use redundant processes, a heartbeat monitor, or a specific authentication mechanism. Such decisions are critical for delivering a system that meets its quality requirements. Despite the stability of high-level decisions, our analysis has shown that tactic-related classes tend to be modified more frequently than other classes and are therefore stronger predictors of change than traditional Object-Oriented coupling and cohesion metrics. In this paper we present the results from this initial study, including an analysis of why tactic-related classes are changed, and a discussion of the implications of these findings for maintaining architectural quality over the lifetime of a software system.