Modularization is almost the only feasible way of implementing large-scale applications. For user interfaces, interactions involving more than one module generate dependencies between modules. In this paper, we present a framework that uses ontologies for building UIs from independent, loosely coupled modules. In an example scenario, we show how that framework is used to build an application for emergency management. Categories and Subject Descriptors D.2.2 [Software Engineering]: Design Tools and Techniques--User Interfaces General Terms Design, Algorithms Keywords Ontologies, User Interfaces, Modularity