  Approaches to self-adaptive software systems use models at runtime to
leverage benefits of model-driven engineering (MDE) for providing views on
running systems and for engineering feedback loops. Most of these approaches
focus on causally connecting runtime models and running systems, and just apply
typical MDE techniques, like model transformation, or well-known techniques,
like event-condition-action rules, from other fields than MDE to realize a
feedback loop. However, elaborating requirements for feedback loop activities
for the specific case of runtime models is rather neglected. Therefore, we
investigate requirements for Adaptation Models that specify the analysis,
decision-making, and planning of adaptation as part of a feedback loop. In
particular, we consider requirements for a modeling language of adaptation
models and for a framework as the execution environment of adaptation models.
Moreover, we discuss patterns for using adaptation models within the feedback
loop regarding the structuring of loop activities and the implications on the
requirements for adaptation models. Finally, we assess two existing approaches
to adaptation models concerning their fitness for the requirements discussed in
this paper.
