A component-based meta-level architecture and prototypical implementation of a reflective component-based programming and modeling language

Component-based Software Engineering studies the design, development and maintenance of software constructed upon sets of connected components. Using existing standard solutions, component-based models are frequently transformed into non-component-based programs, most of the time object-oriented, for run-time execution. As a consequence many component-level descriptions (part of code), e.g. explicit architectures or ports declarations, vanish at the implementation stage, making debugging, transformations or reverse-engineering difficult. It has been shown that component-based programming languages contribute to bridge this gap between design and implementation and to provide a conceptual and practical continuum to fully develop applications with components. In this paper we go one step further in this direction by making a component-oriented programming and modeling language truly reflective, thus making verification, evolution or transformation stages of software development part of this new continuum. The gained reflection capabilities indeed make it possible to perform architecture checking, code refactoring, model transformations or even to implement new languages constructs with and for components. The paper presents an original executable meta-level architecture achieving the vision that "everything is a component}' and an operational implementation demonstrating its feasibility and effectiveness. Our system revisits some standard solutions for reification in the component's context and also handles new cases, such as ports reification, to allow for runtime introspection and intercession on components and on their descriptors. We validate these ideas in the context of an executable prototypical and minimal component-based language, named Compo, whose first goal is to help imagining the future.