We propose a generic presentation system for adaptive educational hypermedia that is highly independent from domain knowledge representation and application state management. Our approach is based on providing a) a module for knowledge representation by means of the definition of domain ontologies that best fit specific domains and/or authors, b) a module for building courses by constructing semantic networks of interrelated domain ontology instances, and c) a presentation module where presentation models (templates and rules) are associated to ontology object classes and relations. By using an explicit presentation model, separate from course contents, course designers are provided with extensive control over the generation of all aspects of presentation, at a moderate development cost. Because minimum assumptions are made about how domain knowledge is structured and updated, our presentation system can be potentially integrated with a wide range of adaptive hypermedia support tools. ...