A federated Web-based multimedia information system on one hand gathers its data from various Web sources, on the other hand offers the end-user a rich semantics describing its content and a userfriendly environment for expressing queries over its data. There are three essential ingredients to successfully deploy such a system. First, one needs a design methodology identifying different design phases and their underlying models which serve as a framework for the designer. Second, there must be

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... set of tools that are able to execute the design, i.e. they serve as the back-end of the information system instantiating the models with data coming from various Web sources. Third, there also must be an entry point for the end-user, where he is able to explore what the system can do for him and where he can formulate his queries. This paper is a follow-up of our previous work describing the Hera design methodology and contributes to all three issues above. In particular, it refines the existing methodology by presenting an explicit RDFS-based integration model and explains how the mediator uses this model to obtain query results. The issue of a user-friendly front-end is addressed by introducing our interface for browsing and querying RDFS-based ontologies.