Within knowledge engineering a new research paradigm is emerging based on the Multi-Agent System (MAS) architectural framework, allowing human and software agents to interoperate and thus cooperate within common application areas. Such a vision entails bridging the different "'views of the world" of knowledgeable agents through the commitment to common definitions of the conceptual entities and of the technical terms employed in knowledge/data bases. We claim that within a multi-agent framework ontological libraries and also standardized terminological repositories should be "'agentified" into ontology and terminology servers providing other agents with the common semantic foundation required for effective interoperation, and allowing the configuration of suitable application ontologies for distributed applications. We restrict our analysis to the case of an organization of cognitive agents, which we'll illustrate with examples from a prototypical health care MAS, that is, a so-called Distributed Healthcare Information System (D-HIS). The prototype makes use of an ontological library written in the standard language Ontolingua.