Abstract: Large scale distributed systems are typically evolving environments that have to deal with interoperability, scalability, mobility and QoS adaptability requirements. Generically, these systems need adaptation mechanisms to cope with short-term (cf. programmed reconfiguration) and long-term requirements (cf. evolutionary reconfiguration). In this paper we propose a reflective component-based framework with architecture style awareness for managing architecture composition and constraining adaptation. Specifically, this framework provides the necessary tools to generate and manipulate the programming model abstractions (i.e. components, connectors and respective properties and interfaces). The framework offers a principled way to deal with both introspection and adaptation of basic and composite components. It provides the developers with the ability to choose, extend and modify architecture style managers. These managers are responsible to represent and check architecture constraints both at development and deployment time, i.e. before any architectural reconfiguration may be committed.