CO-Protégé is a set of plugins that extends Protégé-2000 in order to support a collaborative developing of an ontology. In Co-Protégé people do not make a direct edition of the shared ontology, but also they change it through the publication of ontological artifact. Co-Protégé users manage simultaneously two ontologies the private ontology and the shared one. Private ontology can be edited in the private workspace as users were working in a stand-alone fashion. There is also a shared workspace where the shared ontology is updated through the publication of ontological contributions, even divergent contribution. Divergent contributions make possible the coexistence of many conceptualizations simultaneously at the shared ontology. They are the resource to discuss the design of an ontology. Most of collaborative edition functionalities are provided through a special tab, the shared-private tab that overlaps both workspaces and allows user to manipulate simultaneously their private and the shared ontology. Figure 1 is a snap-shot of the interface of Co-Protégé when a user has already logged into the system.