Stella Gatziu

Events in an Active Object-Oriented Database System

In this paper we investigate the definition, detection, and management of events in the active object-oriented database system SAMOS. First, we present various event specification facilities based on simple but nevertheless powerful constructs which support the modelling of time aspects as well. Second we show how events can be detected in an efficient way. Finally, we deal with the internal representation of events using the benefits of the underlying data model.

Detecting composite events in active database systems using Petri nets

The detection of events in an active database system turns out to be a difficult problem due to the expressive event specification languages proposed in the recent past which include, among others, complexly defined events (composite events). Therefore, a mechanism is required that is suitable to model the semantics of composite events and to implement the event detector. We demonstrate how Petri nets can be used as the basis of such a mechanism in the context of the SAMOS active database system prototype.<<ETX>>

Investigating Termination in Active Database Systems with Expressive Rule Languages

The powerful functionality that active mechanisms add to database management systems presents, besides many advantages, a number of problems related to the control of their behavior. This paper deals with one of these problems: the termination of rule execution. We explain the termination aspect and the aim of termination analysis. Then, we present our approach for investigating the termination of rule execution. In contrast to others, this approach also addresses expressive rule languages as they have been proposed for various recent active database management system prototypes.

The SAMOS active DBMS prototype

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.

The SIRIUS Approach for Refreshing Data Warehouses Incrementally

Data warehouse refresh incorporates issues on how to capture and propagate updates occurring in operational systems into the warehouse in order to keep the data warehouse up-to-date. In this paper, we propose an object-oriented approach for the incremental refresh of data warehouses which considers the special nature of warehouse data, e.g., its temporal and heterogeneous dimension. Our approach can be used for the integration of data from a wide variety of heterogeneous operational sources and independently of a particular database system used for storing the warehouse data.

A Designer's Benchmark for Active Database Management Systems: oo7 Meets the BEAST

A benchmark for active database management systems is described. We are particularly interested in performance tests that help to identify performant and inefficient components. Active functionality that is relevant with respect to performance is identified, and a series of tests is designed that measure the efficiency of the performance- critical components. Results obtained from running the benchmark for a concrete system are presented.

Design and management of data warehouses report on the DMDW'99 workshop

The idea of building data warehouses as central data collections made available for decision support applications in a company is widely accepted. The concrete design and management of a data warehouse from a technical as well as from an organizational point of view, however, turns out to be far from trivial but requires sophisticated and time consuming efforts. The DMDW workshop was held at the CAiSE’99 conference in Heidelberg on June 14-15, 1999. It had the intention to bring together practitioners and researchers to discuss the design and management of data warehouses. The various presentations gave a broad view on the data warehouse life cycle covering aspects relevant at design time, at build time and at run time. Overall, DMDW’99 was recognized as a success. The 30+ participants enjoyed the high quality program (acceptance rate of 50 percent) and had vivid discussions. In this report, we review the presentations given at the DMDW workshop and present some open problems which we believe should be addressed by future research and whose solution could contribute to make data warehouse research more relevant to the practice.

Eine Ereignissprache für das aktive, objektorientierte Datenbanksystem SAMOS

Aktive Datenbanksysteme (aDBS) basieren auf Ereignis/Bedingung/Aktions-Regeln (ECA-Regeln), mit deren Hilfe dem System mitgeteilt wird, wie es bei Eintreten bestimmter modellierter Situationen reagieren soll. Besonders den fur die Formulierung von Ereignissen angebotenen Konzepten kommt dabei hohe Bedeutung fur die Leistungsfahigkeit des Systems zu. In diesem Papier wird die Ereignissprache von SAMOS, einem aktiven, objektorientierten Datenbanksystem, prasentiert, welche die Modellierung mehrerer Arten komplexer Umweltsituationen als Ereignisse ermoglicht.

Modeling and Maintaining Histories in Data Warehouses

The topic of data warehousing [2,4] comprises architectures, algorithms, models, tools, organizational and management issues for integrating data from several operational systems in order to provide information for decision support, e.g., using data mining techniques or OLAP (on-line analytical processing) tools. Thus, in contrast to operational systems which contain detailed, atomic and current data accessed by OLTP (on-line transactional processing) applications, data warehousing technology aims at providing integrated, consolidated and historical data stored in a separate database, the data warehouse (DWH). A data warehouse system (DWS) includes the data warehouse and all components responsible for building, accessing and maintaining the DWH. 6 References

Data Warehouse Refreshment Using SIRIUS

Data warehouse refreshment is often viewed as a problem of maintaining materialized views over operational sources. In this paper, we show that the data warehouse refreshment process is a complex process comprising several tasks, e.g., monitoring, extracting, transforming, integrating and cleaning operational data, deriving new data, building histories and loading the data warehouse. We propose a novel approach for defining and executing the refreshment process based on specifications stored in an object-oriented metadata repository. Our approach considers the multidimensional character of OLAP data and can be used in conjunction with various operational sources and target data warehouses.