When trying to obtain semantical interoperability between different information systems, the integration of heterogeneous information sources is a fundamental task. An important step within this process is the formulation of an integration mapping which specifies how to select, integrate and transform the data stored in the heterogeneous local information sources into a global data store. This integration mapping can then be used to perform the data integration itself. In this paper, we present a UML-based approach to define integration mappings. To this end, we introduce a UML profile which can be used to map local information schemata onto one global schema thus eliminating schema conflicts. We claim that this is the first time that the integration mapping can be specified within the UML model of the application and that this model can be used to generate a working implementation of the schema mappings using MDA-transformations.