Abstract. In this paper we describe the architecture of the MIND system for federating multimedia digital libraries. MIND integrates heterogeneous, multimedia non-co-operating digital libraries and gives the user the impression of a single coherent system. The architecture consists of a single mediator and one proxy (composed of several proxy components) for every connected library. These specialised, distributed components are connected via SOAP. This architecture with clearly defined responsibilities perfectly fits the needs of a distributed research project, and allows for integrating different platforms and programming languages.