This paper suggests that more powerful data base systems (DBMS) can be built by supporting data base procedures as full fledged data base objects. In particular, allowing fields of a data base to be a collection of queries in the query language of the system is shown to allow complex data relationships to be naturally expressed. Moreover, many of the features present in objectoriented systems and semantic data models can be supported by this facility. In order to implement this construct, extensions to a typical relational query language must be made and considerable work on the execution engine of the underlying DBMS must be accomplished. This paper reports on the extensions for one particular query language and data manager and then gives performance figures for a prototype implementation. Even though the performance of the prototype is competitive with that of a conventional system, suggestions for improvement are presented. 1. INTRODUCTION Most current data base systems store inf...

The object-oriented paradigm of computing has started to have a significant influence on many areas of information and data processing, including database systems. This thesis focuses on the various issues and aspects governing the implementation design and development of the object model for TIGUKAT 1 , an object management system which is intended to be a full featured object-oriented database system on completion. The TIGUKAT object model [25] is behaviorally defined with a uniform object semantics. The model is behavioral in the sense that all access and manipulation of objects is restricted to the application of behaviors on objects, and it is uniform in that every entity within the model has the status of a first-class object. Various implementation design alternatives are discussed and the approaches that were chosen are justified. The ensuing implementation provides a robust kernel around which the rest of the system may be conveniently synthesized. 1 TIGUKAT(tee-goo-kat) i...

We present and discuss a modeling approach that supports event-based modeling of information and activity in information systems. Interacting human actors and IT-actors may carry out such activity. We use events to create meaningful relations between information structures and the related activities inside and outside an ITsystem. We use event-activity diagrams to model activity. Such diagrams support the modeling of activity flow, object flow, shared events, triggering events, and interrupting events.

this paper we give an overview of research on extensions of relational database technology. In order to systematically classify different ways to extend the data model we take a programming language point of view of data models: a data model consists of a set of basic (predefined) types, a set of type constructors (or structuring primitives), and a set of operators (for the predefined as well as constructed types). Extensions to each of of these data model constituents are possible and have indeed been investigated in the past. Our presentation focuses on extensions to the type system (primitives and constructors) and those extensions to the operators that are implied by them. During the 1980's, there has been a significant trend in database research addressing the problem of supporting non-traditional database applications. Though relational database systems (RDBMSs) entered the commercial marketplace in the early eighties, it seemed clear that, at least without major enhancements, they would not be appropriate for non-business applications. Several research groups started out to either enhance RDBMS technology in several ways or to develop completely different models and systems. Throughout this paper we limit our scope to those investigations that tried to keep some of the characteristics of the relational model and/or systems. Attempts to make semantic data models operational, for instance, Entity-Relationship models, have already been discussed in this volume before. Also, extensions in query languages' expressive power to deal with recursion, will be surveyed in a subsequent series of articles, as will the object-oriented approaches. Therefore, we will take a more "conservative" approach, that is, stay closer within the original relational framework. The relationa...

w 'W w.u