Principles of Object Oriented

The design of complex information systems requires a transparent model-based methodology. It has been claimed that object orientation will have a signiicant impact on the development of such a methodology, especially as reusability and naturality of conceptual modelling are concerned. The methodology presented in this paper concentrates on four signiicant principles of object oriented database (OODB) design. The basic constituent is step-wise reenement, i.e. to begin the design process with a partial model that is completed and concretized furtheron depending on the growth of application knowledge. Class abstraction, i.e. to support libraries of incomplete parameter-ized designs that are instantiated and specialized later, is a natural consequence hereof. Declarativity is achieved by constraint centered design with (up to some degree) automatic transformation into consistent transactions. Variations enable the design of information systems with heavy reuse of existing design components. The methodology is based on a theoretically founded object oriented datamodel (OODM). Hence the support of inferences such as deciding the identiiability of objects, detecting the relation of an intended design to components in existing design libraries, and checking operations for reducedness as a prerequisite for the automatic transformation of constraints into consistent transactions. The design of data and knowledge intensive information systems requires a transparent model-based methodology. Classically there exist seperate methods for the database and transaction design without a satisfactory integration 7, 9]. Therefore, it is a natural hope that the use of object oriented design methods will improve the situation. Object orientation involves the isolation of data in semi-independent modules in order to promote high software development productivity. This idea stems from programming languages and most methods proposed so far 3, 6, 11, 20] are intended to support object oriented program development. The main diierence in object oriented database (OODB) design is due to the notion of object that is now intended to serve as a basic unit of persistent data, a view that is influenced by semantic datamodels 9]. Since classes then serve not only as behaviour abstractions but also as (persistent) data collections, we have to cope with object identiication, whereas in object oriented programming a simple identiication mechanism via object names is suucient. This makes OODB design a signiicantly diierent task to object oriented program development, although some ideas of the approaches to the latter eld can be taken over.