Information retrieval is content based where the formulation of a request is based on what contain the required documents. Even when a user succeeds in formulating his request, the answers of the system are not always relevant. In information retrieval, the concept of relevance is related to the concepts of noise and silence. Our objective in this paper is to propose a synthesis of the difficulties that can encounter a user in information retrieval. This synthesis should make it possible to the researchers to direct their studies towards the topics not yet completely discussed to provide relevant information and to be used as reference in a context of co-operative search for information. || La recherche documentaire est basée sur le concept de recherche par le contenu où la formulation d'une requête est basée sur ce que contiennent les documents recherchés. Quand un utilisateur parvient à formuler sa requête, les réponses du système ne sont