The working group Didactics of Informatics at the University of Paderborn (Germany) develops and evaluates a multimedia exploration platform for information systems (MEPIS) to the needs of teaching and learning informatics at secondary schools. This paper describes the basic ideas within a system-oriented approach of didactics of informatics and two of its most relevant ideas: the perception of a socio-technical information system and the concept of deconstruction. The pedagogical and technical requirements of developing multimedia tools and integrating them into teaching and learning processes informatics is outlined, and the demands on a multimedia-based exploration environment for the process of deconstruction is described. Finally, a concept of evaluation of teaching and learning processes in informatics under the perspective of a system-oriented didactical approach and the practical use of an exploration platform at secondary schools is presented. (Contains 11 references.) (Author/AEF)