This chapter shows how specifications of mobile multimedia applications can be checked against usability principles very early in software development through an analytic approach. A model-based representation scheme keeps transparent both, the multiple components of design knowledge as well as their conceptual integration for implementation. The characteristics of mobile multimedia interaction are captured through accommodating multiple styles and devices at a generic layer of abstraction in an interaction model. This model is related to context representations in terms of work tasks, user roles and preferences, and problem-domain data at an implementation-independent layer. Tuning the notations of the context representation and the interaction model enables, prior to implementation, to check any design against fundamental usability-engineering principles, such as task conformance and adaptability. In this way, also alternative design proposals can be compared conceptually. Consequently, not only the usability of products becomes measurable at design time, but also less effort has to be spent on user-based ex-post evaluation requiring re-design.