Separation of concerns is one of the key principles in design of complex software systems, which states that individual concerns must be identified and separated in software systems to increase various quality attributes such as maintainability and reusability. Various kinds of module abstractions such as functions, procedures, objects, aspects and event modules have been proposed to facilitate the realization of this principle. Likewise, several composition mechanisms such as method call, event-based communication, joint points/pointcuts, and polymorphism have been proposed to facilitate integrating modules to form the intended software. Software engineers are in an era that have to deal with software systems that must inevitably support some kinds of self-adaptation, have to deal with systems of systems that consist of many independently developed and managed software systems, and have to deal with massively parallel and distributed software systems.