The conception of the method interpreter of the object-oriented database management system

Object-oriented database technology forms an important direction in modern databases. Although there are application domains where today's relational products are inadequate, the main stimulus for investigation of the idea of incorporating object principles into database systems was object-oriented programming. The basic idea in both object-oriented programming and object-oriented database systems is the same - users should not to deal with machine-oriented constructs such as bits, bytes, records and fields, but rather should be able to use objects and operations on them which is the way closer to his/her perception of the real world. No matter of the fact that not only experimental, but also commercial object-oriented database management systems or extended relational systems with object features are available today (e.g. Gemstone, ODE, O2, ObjectStore, Postgress), object-oriented database technology is still intensively developed and improved. An object-oriented database management system (OODBMS) is also developed at our department under a project supported by the Czech grant agency. A language called VDL is used in this system for the database object scheme definition including object types methods implementation. The system consists of several components which enable to define database scheme and implementation of methods, to compile it into an internal representation, provide an access to the database, make possible to navigate over the structure of objects using graphical user interface etc. One of these components is a module that interprets an internal representation of methods of object types. This component is called the method interpreter. Some basic features of the VDL language and the conception of the method interpreter are discussed in this paper.