The SAMOS Active DBMS Prototype

Stella Gatziu, Andreas Geppert, Klaus R. Dittrich

Institut f?r Informatik, Universit?t Z?rich1

Technical Report 94.16

Abstract
We describe SAMOS, an active object-oriented database management system prototype. SAMOS offers a powerful rule definition language, including a small yet powerful set of event definition facilities. It is able to detect primitive and composite events automatically and efficiently. Upon event detection, SAMOS executes rules attached to the occurred events.

1 Introduction

Active database management systems (aDBMSs) [1] have recently found great interest as a topic of database research, and restricted aDBMS-functionality is even offered by some commercial relational systems.

An aDBMS implements ?reactive behavior? in that it is able to detect situations in the database and to perform corresponding actions specified by the user. Applications that require such reactive behavior are thus freed from performing ?polling? in order to detect interesting situations and from encoding reactions (possibly redundantly) in applications.

SAMOS2 [2, 3] is our home-grown active object-oriented database management system whose development has been started in 1991. To a large extent, SAMOS is operational now and thus is among the first demonstratable active object-oriented DBMSs.

The prototype implementation of SAMOS is characterized by a layered architecture. All active components are built ?on top? of a passive object-oriented database system, which is left unmodified and is a black box for SAMOS. This is in contrast to integrated architectures, where the kernel DBMS can be internally modified. The reason for applying the layered approach in SAMOS is the shorter implementation time in comparison to the integrated architecture, since the passive part can be reused in its entirety. Additionally, an open or configurable DBMS has not been available at the time the project started.

1. Authors? address: Institut f?r Informatik, Universit?t Z?rich, Winterthurerstr. 190, CH-8057 Zurich, Switzerland. Fax: +41-1-363 0035, Email: {gatziu | geppert| dittrich}@ifi.unizh.ch
2. Swiss Active-Mechanism based Object-oriented database System