This thesis deals with the externalization of change management knowledge in the National French Railways Company for sharing (elicitation, modelling and formalization). We have chosen to consider not only the «implicit» dimension of this know-how (which is not stated) but also its "pre-reflective" dimension (which is not immediately conscious for the subject who uses it). This approach has led us to investigate a "pre-reflective knowledge engineering". Currently, most knowledge management researchers and practitioners prefer to solve the problem of tacit sharing by socialization rather than by externalization. However there has been some research done on eliciting knowledge which could be applied to knowledge management. More precisely, we have focused on the contributions of the “explicitation interview” (Vermersch) to knowledge management problems. Our research went through the following stages: state of the art in change management, knowledge management and pre-reflective knowledge, description of the system constituted by the change management knowledge at the SNCF, design of an ontology in order to represent this explicit, implicit and pre-reflective knowledge through conceptual graphs, design and development of a server for this knowledge sharing and finally, the elicitation and formalization of the know-how which consists in leading participative working parties. Methodologically, this study has enabled us to develop on the one hand a method for building an ontology starting from pre-reflective knowledge, on the other hand an adaptation of the explicitation interview for the knowledge management domain
