Characterizing Architectural Drifts of Adaptive Systems

An adaptive system (AS) evaluates its own behavior and changes it when the evaluation indicates that the system is not accomplishing what it is intended to do, or when better functionality or performance is possible. MAPE-K is a reference model that prescribes the adaptation mechanism of ASs by means of high-level abstractions such as Monitors, Analyzers, Planners and Executors and the relationships among them. Since the abstractions and the relationships provided by MAPE-K are generic, other reference models were proposed focusing on providing lower level abstractions to support software engineers in a more suitable way. However, after the analysis of seven representative ASs, we realized the abstractions prescribed by the existing reference models are not properly implemented, thus leading to architectural drifts. Therefore, in this paper we characterized three of these drifts by describing them with a template and showing practical examples. The three architectural drifts of ASs are Scattered Reference Inputs, Mixed Executors and Effectors, and Obscure Alternatives. We expect that by identifying and characterizing these drifts, we can help software architects improve their design and, as a consequence, increase the reliability of this type of systems.