Designing ontologies that could be shared for developing ontology-based learning environments is still a challenge. The overall aim of the OURAL project was to provide a case study on common ontology design. It brought together researchers and practitioners from different domains (educational science, computer science, and cognitive psychology). We benefited from several on going field studies launched to identify authors and tutors needs and to prototype ontology-based services providing answers to the identified needs. In this paper, we describe the context of the project, the case studies that have been chosen, the focus on helping the teacher in describing "learning situations", the resulting ontology as well as the principles we used and some conclusions about ontology elicitation and reuse from these case studies.