Revising a Security Tactics Hierarchy through Decomposition, Reclassification, and Derivation

Software architecture is the set of important design decisions that address cross-cutting system quality attributes such as security, reliability, availability, and performance. Practitioners often face difficulty in beginning an architectural design due to the lack of concrete building blocks available to them. Tactics are fundamental design decisions and play the role of these initial design primitives and complement the existing design constructs such as architectural or design patterns. A tactic is a relatively new design concept, and tactics repositories are still being developed. However, the maturity of these repositories is inconsistent, and varies depending on the quality attribute. To address this inconsistency and to promote a more rigorous, repeatable method for creating and revising tactics hierarchies, we propose a novel methodology of extracting tactics. This methodology, we claim, can accelerate the development of tactics repositories that are truly useful to practitioners. We discuss three approaches for extracting these tactics. The first is to derive new tactics from the existing ones. The second is to decompose an existing architectural pattern into its constituent tactics. Finally, we extract tactics that have been misidentified as patterns. Among the many types of tactics available, this paper focuses on security tactics. Using our methodology, we revise a well-known taxonomy of security tactics. We contend that the revised hierarchy is complete enough for use in practical applications.