Résumé
RDFS is a knowledge representation language developped for the Semantic Web by the World Wide Web Consortium (W3C). Objects of this language (labelled graphs) are given formal model-theoretic semantics, allowing to define the subsumption relation between RDFS documents. In this paper, we reformulate subsumption into a kind of labelled hypergraphs homomorphism called projection. The huge similarities between this projection and the one defined for conceptual graphs allow us to translate many theoretical results and algorithms.