Résumé: Forums on the Internet are an overwhelming source of knowledge considering the number of topics treated and users who participate in these discussions. This volume of data is difficult to comprehend for a person with respect for the large number of posts. Our work proposes a new formal framework for synthesizing information contained in these forums. We extract a social network that reflects reality by extracting multiple relationships between individuals (structural relationship, name and text quotation relationships). These relationships are created from the structure and the content of the discussion. Results show that discovering quotation relationships from forums is not trivial.