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Abstract. Architectural design has been characterized as making a series of decisions that have system-wide impact. These decisions have side effects which can have significant impact on the system. However, the impact may be first understood much later; when the system architecture is difficult to change. Architecture patterns can help architects understand the impact of the architectural decisions at the time these decisions are made, because patterns contain information about consequences and context of the pattern usage. However, this information has been of limited use because it is not presented consistently or systematically. We discuss the current limitations of patterns on evaluating their impact on quality attributes, and propose integrating the information of patterns' impact on quality attributes in order to increase the usefulness of architecture patterns.

a b s t r a c tSoftware architecture designers inevitably work with both architecture patterns and tactics. Architecture patterns describe the high-level structure and behavior of software systems as the solution to multiple system requirements, whereas tactics are design decisions that improve individual quality attribute concerns. Tactics that are implemented in existing architectures can have significant impact on the architecture patterns in the system. Similarly, tactics that are selected during initial architecture design significantly impact the architecture of the system to be designed: which patterns to use, and how they must be changed to accommodate the tactics. However, little is understood about how patterns and tactics interact. In this paper, we develop a model for the interaction of patterns and tactics that enables software architects to annotate architecture diagrams with information about the tactics used and their impact on the overall structure. This model is based on our in-depth analysis of the types of interactions involved, and we show several examples of how the model can be used to annotate different kinds of architecture diagrams. We illustrate the model and annotation by showing examples taken from real systems, and describe how the annotation was used in architecture reviews. Tactics and patterns are known architectural concepts; this work provides more specific and in-depth understanding of how they interact. Its other key contribution is that it explores the larger problem of understanding the relation between strategic decisions and how they need to be tailored in light of more tactical decisions.

0 7 4 0 -7 4 5 9 / 1 4 / $ 3 1 . 0 0 © 2 0 1 4 I E E E J a n u a r y / F e b r u a r y 2 0 1 4 | // Architecture evaluation is an important activity in the software engineering life cycle, but unfortunately, it isn't regularly practiced in industry. Decision-centric architecture reviews uncover and evaluate the rationale behind the most important architecture decisions.Experiences in large industrial projects have shown that full-scale DCAR evaluations, including reporting, can be conducted in fewer than five person-days while still producing satisfying results for stakeholders. //