The role of conceptual modeling in Educational Adaptive Hypermedia Applications (EAHA) is especially important. A conceptual model of an educational application depicts the instructional solution that is implemented, containing information about concepts that must be ac-quired by learners, tasks in which learners must be involved and resources that will be used. The importance of such a model is multifold. It formally depicts the outcomes of instructional analysis, drives the development of actual applications and provides the information basis for automatic application generation in the context of Adaptive and Intelligent Tutoring Systems. In this paper we begin by describing a method for designing EAHA. Our method uses UML as the modeling language and defines the design process in three distinct steps. We propose an RDF encoding of the Conceptual Model, which is the outcome of the first step, following a specific RDF schema that is appropriate for such applications. This encoding can be obtained automatically and, in this way, a machine processable semantic description of the EAHA becomes available, as an outcome of the design process. In the resulting RDF-encoded Conceptual Model, we define rules of adaptation using the existing language RuleML. (Contains 8 figures.)