In 1986, van Rijsbergen promotes a principle in which the matching between a query and a document is founded on a form of plausible, or uncertain logical inference. His formulation was deliberately abstract, no attempt was made to specify how such a principle might be implemented through an effective logic and under a particular semantics. In classical logics inference is often associated with logical implication: a document d is relevant to a query q if it implies the query, so if d -> q is true. This mechanism is too strict to be useful in the matching process. In order to overcome this problem, the possible worlds semantics seems to be a good way to formalize the uncertain inferences needed in an information retrieval system. Thus, in 1988 Nie initiated a work which has as its basic assumption the consideration that a document can be associated to a possible world. We think however that a more refined approach must be adopted especially when complex information are considered. It is based on the notion of facet, which allows to consider a document under several points of view, every one being associated to a possible world. Our claim here is that the conceptual graphs formalism is enough powerful to implement such a refined approach, in a way that captures the notion of uncertainty and that explains the retrieval process in terms of the possible worlds semantics.