Information Systems adaptation to its users require s to be able to identify real uses made of the syst em. The behaviour models, extracted from System-User interaction traces, provide representations of the real tasks performed in the Information System. We propo se to exploit these representations in order to extract knowledge that can, in turn, help to suppor t users in their activities or to adapt the system to emerging activities. This paper describes such an a pproach we applied in the field of Information Retrieval by navigation in hypermedia. The behaviour models consist of navigational patterns and extracted knowledge is a thesaurus whose content is strongly related to the context of the available information. The paper is focused on the process of relation extraction between terms. It also present s experiments carried out for testing relevance of th ese representations. We show that by using the associations of the thesaurus and