Data dictionaries in open system communication

My current work is based on the premise that one should be able to access a foreign database system with the same ease that one can move from one type of telephone system to another. Data dictionaries must form the focal point in any architecture which would support such a concept. Data from a foreign system must be presented to the local system in such a way that the local system can understand it if the databases are disjoint, or merge the foreign conceptual model with the local one if the data bases have some common structure. Once such a rapport has been established, other aspects of the conceptual models, such as constraints and operations on the data, must be translated from one system to the other. This raises the following issues which I would like to see discussed at the workshop.