Lean languages and models: Towards an interoperable kernel for persistent object systems

Reliable interoperation between independently developed systems frequently requires type-safe access to persistent data objects and generic services while today's system architectures and interoperation tools still focus primarily on store-level access to volatile data and simple monomorphic or untyped services. The authors summarize experience gained in a long-term project that provides persistence abstractions and generic database support in a strongly typed database environment which includes optimizing gateways to commercial relational database servers. They make use of a uniform language model based on higher-order polymorphic types to capture the essential interoperation semantics including classical cross-language calling mechanisms, remote procedure call models as well as relational and object-based database gateways. This uniform language model is also the conceptual core of the Tycoon database environment being developed at Hamburg University. Tycoon lifts persistent object system interoperability to a higher level of genericity and precision while further reducing overall system complexity by a lean approach to languages and models for data, execution and storage. Since it is central to the concept of lean production to substantially reduce the manufacturing penetration by importing and reusing external services, interoperability is crucial.