Using the term service for the abstract contract concluded between a service requester and a service provider, three diferent data schemas have to be iden- tified, namely the requester's schema, the provider's schema and the reference schema introduced by the ser- vice specification.

Metamodeling and schema transformation ap- proaches from the area of model driven architecture can be used to define these schemas and their mappings as well as the appropriate transformations that have to be applied to the data.

This paper explains an approach towards metamodel- based service interoperability along an extended exam- ple of providing visualization services for the Bauhaus re-architecting tool.