Cloud computing has become more and more popular. Many companies (viz., cloud providers) are outsourcing their IT resources into clouds so that users can hire those resources only if they really need the resources and give the resources back when they do not need the resources any longer. This creates a new challenge for cloud providers - they need to provide users with systems, which can automatically assign IT resources on the fly. These systems should give the possibility to evaluate events from different event sources at one or more external coordination points. These points can coordinate the usage of the IT resources in clouds. Thus, the systems should use active mechanisms for the coordination (e.g., scalability) of IT resources in cloud environments.