This article describes BOOM, an object-oriented fourth-generation system. BOOM supports the powerful and elegant development of information systems in an object-oriented manner. By using object-oriented techniques, the complexities in building information systems can be handled more easily, and the development process in general can be improved and revived. BOOM decouples development from the physical environment. BOOM developers build a logical object-oriented data model that, after development, is automatically transferred into a relational database system. The toolset supplied for the construction of information systems includes components for the definition of structural object-oriented data models, for the generation of user interfaces. and the arrangement of application logic. Generic operations for manipulating user-defined objects are provided for every BOOM application. BOOM objects are stored in a relational database and are dynamically loaded on demand. Further, how the object model is transformed to relational tables is illustrated.