Making a database system active entails developing an expressive event specification language with well-defined semantics, algorithms for the detection of composite events, and an architecture for an event detector along with its implementation. Thii paper presents the semantics of composite events using the notion of a global event history (or a global event-log). Parameter contexts are introduced and precisely defined to facilitate efficient management and detection of composite events. Finally, an architecture and the implementation of a composite event, detector is analyzed in the context of an object-oriented active DBMS. 1

Event based monitoring is critical for managing and debugging networks and distributed systems. This paper presents GEM -- an interpreted Generalised Event Monitoring language. It allows high level, abstract events to be specified in terms of combinations of lower level events from different nodes in a loosely coupled distributed system. Event monitoring components can thus be distributed within the system to perform filtering, correlation and notification of events close to where they occur and thus reduce network traffic. GEM is a declarative rule based language in which the notion of real time has been closely integrated and various temporal constraints can be specified for event composition. The paper discusses the effect of communication delays on composite event detection and presents a tree-based solution for dealing with out-of-order event arrivals at event monitors. Keywords: Monitoring distributed systems, event reporting, event correlation, event filtering, composite event...

Reactivity on the Web is an emerging research issue covering: updating data on the Web, exchanging information about events (such as executed updates) between Web sites, and reacting to combinations of such events. Reactivity plays an important role for upcoming Web systems such as online marketplaces, adaptive, Semantic Web systems as well as Web services and Grids. After motivating the need for reactivity on the Web through an application scenario, this article introduces the paradigms upon which the high-level language XChange for programming reactive behaviour and distributed applications on the Web relies. Then, it briefly presents the main syntactical constructs of XChange. Finally, it sketches the implementation of a reactive Web-based application in XChange. 1

Abstract. Event-based monitoring is critical for managing and debugging networks and distributed systems. This paper presents GEM—an interpreted generalized event monitoring language. It allows high-level, abstract events to be specified in terms of combinations of lower-level events from different nodes in a loosely coupled distributed system. Event monitoring components can thus be distributed within the system to perform filtering, correlation and notification of events close to where they occur and thus reduce network traffic. GEM is a declarative rule-based language in which the notion of real time has been closely integrated and various temporal constraints can be specified for event composition. The paper discusses the effect of communication delays on composite event detection and presents a tree-based solution for dealing with out-of-order event arrivals at event monitors. 1.

distributed computing services that essentially abstract the underlying network services to a monolithic “black box. ” In a mobile operating environment, the fundamental assumption of middleware abstracting a unified distributed service for all types of applications operating over a static network infrastructure is no longer valid. In particular, mobile applications are not able to leverage the benefits of adaptive computing to optimize its computation based on current contextual situations. In this paper, we introduce the Mobile Platform for Actively Deployable Service (MobiPADS) system. MobiPADS is designed to support context-aware processing by providing an executing platform to enable active service deployment and reconfiguration of the service composition in response to environments of varying contexts. Unlike most mobile middleware, MobiPADS supports dynamic adaptation at both the middleware and application layers to provide flexible configuration of resources to optimize the operations of mobile applications. Within the MobiPADS system, services (known as mobilets) are configured as chained service objects to provide augmented services to the underlying mobile applications so as to alleviate the adverse conditions of a wireless environment. Index Terms—Middleware, mobile applications, mobile computing support services, mobile environments. 1

We have extended an Interface Definition Language to handle event registration and notification. Clients register interest in specified classes of events and servers then notify them of any occurrence asynchronously. Event occurrences are identified by parameters which conform to IDL typing constraints and can therefore be used in synchronous method invocations. Methods to handle registration and notification are generic and can be inherited by objects of any class: as a by-product of IDL processing the stubs to handle event creation and decoding are generated automatically. We have implemented a prototype composite event recogniser based on non-deterministic finite state machines. Initial experience with this prototype is encouraging. 1 Introduction The term "event" is used in many spheres of computing to capture the notion of an autonomous asynchronous occurrence. Here, we are concerned with events within an object-orientated distributed programming (OODP) environment and have des...

With the increasing complexity of enterprise networks and the Internet, event correlation is playing an increasingly important role in network as well as integrated system management systems. Even though the timing of events often reveals important diagnostic information about event relationships and should therefore be represented in event correlation rules or models, most extant approaches lack a formal mechanism to define complex temporal relationships among correlated events. In this paper, we discuss the formal use of composite events for event correlation and present a composite event specification approach that can precisely express complex timing constraints among correlated event instances, for which efficient compilation and detection algorithms have been developed in [14, 13]. A Java implementation of this approach, called Java Event CorrelaTOR (JECTOR), is described, and some preliminary experimental results of using JECTOR in an experimental network management environment ...

Making a database system active entails not only the specification of expressive ECA (eventcondition -action) rules, algorithms for the detection of composite events, and rule management, but also a viable architecture for rule execution that extends a passive DBMS, and its implementation. In this paper, we propose an integrated active DBMS architecture for incorporating ECA rules using the Open OODB Toolkit (from Texas Instruments, Dallas). We then describe the implementation of the composite event detector, and rule execution using a nested transaction model for object-oriented active DBMS. Finally, the functionality supported by this architecture and its extensibility are analyzed along with the experiences gained. 1 Introduction During the last decade, database management systems (DBMSs) have evolved considerably to meet the requirements of emerging applications. ECA rules (or event-condition-action or situation-action rules) generalize the forms of monitoring supported earlier (e...

Making a database system active entails developing an expressive event specification language with well-defined semantics, algorithms for the detection of composite events, and an architecture for an event detector along with its implementation. This paper presents Snoop as the event specification language along with the semantics of composite events over a global event-history (or a global event-log). Parameter contexts are introduced for meaningfully restricting the detection of composite events. In addition, algorithms for the detection of composite events in various parameter contexts are presented. Finally, an architecture and implementation of a composite event detector is analyzed in the context of an object-oriented active DBMS. 1 Introduction Consensus is emerging in the database community about the structure of rules for supporting active functionality. A rule consists, primarily, of three components: an event, a condition, and an action. A rule consisting of these component...

Abstract. Distributed publish/subscribe systems are naturally suited for processing events in distributed systems. However, support for expressing patterns about distributed events and algorithms for detecting correlations among these events are still largely unexplored. Inspired from the requirements of decentralized, event-driven workflow processing, we design a subscription language for expressing correlations among distributed events. We illustrate the potential of our approach with a workflow management case study. The language is validated and implemented in PADRES. In this paper we present an overview of PADRES, highlighting some of its novel features, including the composite subscription language, the coordination patterns, the composite event detection algorithms, the rule-based router design, and a detailed case study illustrating the decentralized processing of workflows. Our experimental evaluation shows that rule-based brokers are a viable and powerful alternative to existing, special-purpose, content-based routing algorithms. The experiments also show that the use of composite subscriptions in PADRES significantly reduces the load on the network. Complex workflowscanbeprocessedinadecentralizedfashionwithagainof40% in message dissemination cost. All processing is realized entirely in the publish/subscribe paradigm. 1