Lehrgebiet Informationssysteme

The VStore DBMS is a prototype implementation of the object and version model OVDM and, therefore, provides the query language OQL at its interface. VStore exploits the object oriented database management system ObjectStore as access system and storage system. VStore's data system is implemented as an additional layer realized on top of ObjectStore. This additional layer maps OVDM structures to C++ structures managed by ObjectStore. Therefore, the tasks of this layer are schema transformation and query transformation. A major component is the OSOQL- compiler directly generating C++ code from OQL statements (DDL as well as DML). Besides the implementation of OVDM concepts by the mentioned transformation approach, we are using VStore as a realization platform for new concepts which can be assigned to the following areas.

An application programming interface (API) supports the development of C++ application programs with embedded OQL queries. The corresponding run-time system (also written in C++) provides checkout/ checkin primitives, adapted hierarchical cursors as well as corresponding operators for object-buffer based manipulation of versioned data.

A graphical user interface supports ad-hoc queries and provides integrated browsing facilities.

VStore provides ACID transactions; transaction management and, especially, concurrency control, however, is determined by the concepts of the CONCORD model.

Thus, the VStore environment is used as a realization platform for the implementation of the CONCORD prototype. As a consequence the CONCORD prototype exploits VStore as data repository.