Object-oriented database systems: The next miles of the marathon

Half a decade or so ago, object-oriented database systems have become an extremely hot topic of database research and development. At many places all over the world, people work on individual aspects or complete system prototypes. Already, some systems have even reached the marketplace. Experience shows, however, that it takes some 15 yr or more until a new software-related technology really makes it towards widespread use in large-scale applications. Obviously, then, the field of object-oriented database systems is not yet in a state where e.g. relational systems are today, and it may even be harder to get there than it has been for these latter kinds of products: there is no such thing like the object-oriented data model, a number of basic issues are still pending (better) solutions, and there is also still vast room for improved implementations. This paper first tries to bring some clarification to the notion of “object-orientation” in the context of database systems, and then elaborates on some selected features and issues where further progress seems to be especially desirable.