Volume 51, Issue 5

This paper retrospectively outlines the progress of event-based capability over the last three decades. It further briefly elaborates the impact of this technology and how it has been adapted for a variety of domains and applications. Although research on event-based approaches started in a humble manner with the intention of introducing triggers in database management systems for monitoring application state and to automate applications by reducing/eliminating user intervention, currently it has become a force to reckon with as it finds use in many diverse domains. This is primarily due to the fact that a large number of real-world applications are indeed event-driven for which this paradigm is the most appropriate.

This paper outlines requirements and sketches techniques for introducing to the publish/subscribe model the capability to uniformly access data produced in the past and future. The new model can filter, aggregate, correlate and project any combination of historic and future data. A flexible architecture is presented consisting of distributed and replicated data repositories that can be provisioned in ways to tradeoff availability, storage overhead, query overhead, query delay, load distribution, parallelism, redundancy and locality.

Event-based systems are used increasingly often to build loosely-coupled distributed applications. With their growing popularity and gradual adoption in mission critical areas, the need for novel techniques for benchmarking and performance modeling of event-based systems is increasing. In this article, we provide an overview of the state-of-the-art in this area considering both centralized systems based on message-oriented middleware as well as large-scale distributed publish/subscribe systems. We consider a number of specific techniques for benchmarking and performance modeling, discuss their advantages and disadvantages, and provide references for further information. The techniques we review help to ensure that systems are designed and sized to meet their quality-of-service requirements.

Complex event processing (CEP) is an emerging software technology for detecting business-relevant situations in streams of events and for providing these detected situations to business processes that are interested in it. While currently CEP-systems are mostly deployed within a single business domain at a limited scale, the cooperative nature of business applications gives reason that complex event processing will soon address multiple business domains and involve an increasingly large number of business events. In order to ensure interoperability as well as efficient utilization of processing and network capability, we motivate the need for heterogeneous correlation technology in the context of business applications. In this article we give an overview of the project “Distributed heterogeneous event processing” (DHEP) involving the IBM Böblingen lab and the Universität Stuttgart, where this need is adressed. The key aspect of the project is the deployment of collections of event correlation rules to a network of heterogeneous event correlation engines. We give an overview of challenges and possible solutions for the dynamic configuration of such environments and present our architecture which supports network-wide cooperation between different correlation engines.

Event-based systems give the potential for active information sharing. The event-based paradigm, if used for event transport, provides loose coupling between components, many-to-many communication and mutual anonymity of event producers and event consumers. This communication style has been adopted enthusiastically for convenience of programming; particularly for financial processing, healthcare applications and sensor-based systems. But some data is sensitive, and its visibility must be controlled carefully for personal and legal reasons. Our research projects have explored this space for some time, investigating application domains in which the event-based paradigm is appropriate yet where security is an issue. We discuss security issues for multi-domain, event-based systems, considering the requirements of applications and the risk associated with failure. We provide an overview of the state-of-the-art in secure event-based systems: research already carried out, work in progress and issues still to be addressed. This is of relevance to emerging large-scale systems required by government and public bodies for domains such as healthcare, police, transport and environmental monitoring.

Due to vast progress of medical image devices, clinicians today rely deeply on images for screening, diagnosis, treatment planning and follow up. However, these medical images are still indexed by keywords and can not be searched and retrieved for their content. In this article we present the project MEDICO that strives to implement intelligent medical image search by means of machine learning algorithms and semantic technologies.

Zusammenfassung Konventionellen Menüdarstellungen in Fahrerinformationssystemen (FIS) mangelt es an einem adäquaten Interaktionsmodell für die typischerweise heterogene Benutzergruppe. Um Attraktivität und Gebrauchstauglichkeit zu erhöhen, wird ein graphischer, metaphernbasierter Ansatz entwickelt. Dreidimensionale Anzeige-Bedienkonzepte sowie kartographische Repräsentationen großer Datenmengen und erklärende Animationen werden aus vertrauten Gegenständen und deren physikalischen Eigenschaften abgeleitet. Eine benutzerbasierte Evaluierung bezüglich Attraktivität, Gebrauchstauglichkeit und Verträglichkeit mit der Fahraufgabe weist empirisch eindeutige Vorteile hinsichtlich der Herausforderungen für FIS nach.