Declarative semantics of interoperable data- and knowledge-bases

We show how the declarative semantics of intelligent and cooperative information systems can be-developed in an institutional framework. The presentation of the semantics is tailored to Epsilon, a management system for distributed knowledge bases whose modules may employ different logical systems, and that allows deductions to be performed interoperatively. The components of an Epsilon knowledge base are theories, and relationships like inheritance between theories are established via so called links. This paper gives a semantic foundation for Epsilon links, indicating the combination of information represented in different formalisms (using mixed institutions) as well as the constraining of the possible models of a theory to those freely generated by another one (using duplex institutions). These categorial concepts are applied to the actual implementation of Epsilon.<>