GEAHS is a platform designed to ease the development of Adaptive Educational Hypermedia. In this document, we explain the underlying principles of this platform. Genericity is achieved thanks to an adaptation engine based on conceptual graphs, situation calculus and RDF. We are currently working on a graphical tool to build an AEH system designed on top of our engine. This paper describes the main aspects of our system, as well as the use we make of standards and recommendations.