The development of highly interactive multimedia applications is still a challenging and complex task. In addition to the application logic multimedia applications typically provide a sophisticated user interface with integrated media objects. As a consequence, the development process involves different experts for software design, user interface design, and media design. There is still a lack of concepts for a structured development process to integrate these requirements. In this paper we introduce the Multimedia Modeling Language ( MML), a visual modeling language supporting the design process in multimedia application development. It is part of a model-driven development approach for multimedia applications. The language is oriented on well-established software engineering concepts, in particular UML 2.0. It integrates the results of two different research lines: application-oriented multimedia modeling and model-based user interface development. In this paper we describe the co...