In this paper we study the role of orchestration and its modeling for interactive systems. After a common sense explanation of orchestration and its meaning in information technologies and mainly SOA, we explain its use specifically for the design and use of interactive systems. We propose a taxonomy and, in relation with it, we point out both adaptation and plasticity of HCI systems as a partial answer for orchestration. We then suggest complementary aspects needed for orchestration and their modeling in an MDA approach. We also present a case study and we conclude by considering perspectives.