The research presented deals with the problem of how information technology can support the interconnection of medical information systems in practice. We apply a two-part structural standard that consists of a fixed Information Reference (IR) Model, and an Archetype Reference (AR) Model that uses the structures of the IR model. A very important problem with the real-world application of such a two-level model is that the high level (abstract) entities, structures and their connections must be somehow translated into lower level equivalents that legacy database information systems can actually use to program their standardised interface. Our choice for the lower level medium is XML, such that the standard appears as an XSD schema that can be used, in the usual way, to validate a message document. To test the viability of the above paradigm, we developed an archetype-XSD translator tool in the form of Protégé/OWL plugins and tested it on an industrial interface for exchanging medical episodes (MedQuery), using an implementation of openEHR. We found that the most important features: Containment, Cardinality, Named references to other instances, and References to external terminologies, could all be mapped to standard XSD constructs. We also developed a validator plugin to check external references. We plan to put the system at work in a heterogeneous medical messaging system (a descendant of the Budapest based MediNet system) in the near future.