The term "Organizational Memory Information System" (OMIS or OM) has been assigned to systems that support the management of explicit knowledge in an organization. In a single OM-scenario a set of agents dedicated to particular management tasks can communicate and collaborate on a semantic level by the presence of a domain ontology acting as a semantic index to the stored information items. In order to support communication and collaboration across OM boundaries, a common understanding of domain specific terms must be established e.g. by developing a shared ontology. In this paper we sketch an evolutionary approach toward a shared ontology based on similarities of local concepts gained by negotiation. We identify three semantic levels of Inter-OM communication and present a generic communication pattern that incrementally moves communication to higher levels.