Ontologies are used as a means of expressing agreements to a vocabulary shared by a community in a coherent and consistent manner. As it happens in the Internet, ontologies are created by community members in a decentralized manner, requiring that they be merged before being used by the community. We develop an algabra to do so in the Resource Discription Framework (RDF). To provide formal semantics of the proposed algebraic operators, we type a fragment of the RDF syntax.