International audienceThis paper describes a project to represent and share tacit change management knowledge. Based on an ontology, this project enables French Railways Company (SNCF)'s project managers to share their know-how through an IT device called "knowledge server". This paper contains two kinds of contributions. The first contribution is the ontology itself. The second contribution is methodological. By describing the ontology's design process, based on a study of project managers' practices, the paper indicates how to build an ontology that refers to tacit knowledge, to human professional know-how
