Abstract : Software Composition techniques improve the reusability of systems built by composing smaller software artifacts. Composition is a challenge for Human Computer Interaction and Software Engineering communities. These communities have proposed metamodeling approaches in order to address composition at a high level and to overcome technological diversity as advocated by the Model Driven paradigm. However, such metamodels cover only one aspect of system composition. This leads to build incomplete systems. To tackle this problem, we propose a global composition approach that takes into account the functional composition choices and that maintains the interaction links between interactive and functional parts of systems. This paper presents the metamodeling on which relies the proposed composition approach.