Current tag modelling does not fully take into account the rich and diverse nature tags, as signs, can take on. We propose an ontology of tags in which tags are modelled as named graphs. These named graphs are made of a resource linked to a "sign" which can be any resource reachable on the Web (an ontology concept, an image, etc.). The purpose of our model is to be able to describe tags in a very general manner, and as an immediate consequence, to describe tags as modelled by other tag models (SCOT, CommonTag, etc.). Our tag model can thus be seen as a bridge between the manifold conceptualizations and instantiations of tags’s models currently available on the Web.