Reactivity on the Web

Reactivity, the ability to detect simple and composite events and respond in a timely manner, is an essential requirement in many present-day information systems. With the emergence of new, dynamic Web applications, reactivity on the Web is receiving increasing attention. Reactive Web-based systems need to detect and react not only to simple events but also to complex, real-life situations. This paper introduces XChange, a language for programming reactive behaviour on the Web, emphasising the querying of event data and detection of composite events

Complex Event Processing (CEP)

Event-driven information systems demand a systematic and automatic processing of events. Complex Event Processing (CEP) encompasses methods, techniques, and tools for processing events while they occur, i.e., in a continuous and timely fashion. CEP derives valuable higher-level knowledge from lower-level events; this knowledge takes the form of so called complex events, that is, situations that can only be recognized as a combination of several events. 1 Application Areas Service Oriented Architecture (SOA), Event-Driven Architecture (EDA), cost-reductions in sensor technology and the monitoring of IT systems due to legal, contractual, or operational concerns have lead to a significantly increased generation of events in computer systems in recent years. This development is accompanied by a demand to manage and process these events in an automatic, systematic, and timely fashion. Important application areas for Complex Event Processing (CEP) are the following

Towards self-protecting ubiquitous systems : monitoring trust-based interactions

The requirement for spontaneous interaction in ubiquitous computing creates security issues over and above those present in other areas of computing, deeming traditional approaches ineffective. As a result, to support secure collaborations entities must implement self-protective measures. Trust management is a solution well suited to this task as reasoning about future interactions is based on the outcome of past ones. This requires monitoring of interactions as they take place. Such monitoring also allows us to take corrective action when interactions are proceeding unsatisfactorily. In this vein, we first present a trust-based model of interaction based on event structures. We then describe our ongoing work in the development of a monitor architecture which enables self-protective actions to be carried out at critical points during principal interaction. Finally, we discuss some potential directions for future work

A language and an execution model for the detection of active situations

This paper presents a thesis about a language and an execution model for the detection of situations aimed at reducing the complexity of active applications. This work has been motivated by the observation that in many cases, there is a gap between current tools that enable to react to a single event (following the ECA: Event – condition – action paradigm), and the reality, in which a single event may not require any reaction, however the reaction should be given to patterns over the event history. The concept of situation presented in this paper, extends the concept of composite event, in its expressive power, flexibility, and usability. This paper motivates the work, surveys other efforts in this are, and presents preliminary ideas for both the language and the execution model

Using UML’s Sequence Diagrams for Representing Execution Models Associated to Triggers

11 pages, 3 figures.-- Contributed to: 23rd British National Conference on Databases (BNCOD 23, Belfast, Northern Ireland, UK, July 18-20, 2006).Using active rules or triggers to verify integrity constraints is a serious and complex problem because these mechanisms have behaviour that could be difficult to predict in a complex database. The situation is even worse as there are few tools available for developing and verifying them. We believe that automatic support for trigger development and verification would help database developers to adopt triggers in the database design process. Therefore, in this work we suggest a visualization add-in tool that represents and verifies triggers execution by using UML’s sequence diagrams. This tool is added in RATIONAL ROSE and it simulates the execution sequence of a set of triggers when a DML operation is produced. This tool uses the SQL standard to express the triggers semantics and execution.This work is part of the project "Software Process Management Platform: modelling, reuse and measurement". TIN2004/07083.Publicad

Temporal Stream Algebra

Data stream management systems (DSMS) so far focus on event queries and hardly consider combined queries to both data from event streams and from a database. However, applications like emergency management require combined data stream and database queries. Further requirements are the simultaneous use of multiple timestamps after different time lines and semantics, expressive temporal relations between multiple time-stamps and exible negation, grouping and aggregation which can be controlled, i. e. started and stopped, by events and are not limited to fixed-size time windows. Current DSMS hardly address these requirements. This article proposes Temporal Stream Algebra (TSA) so as to meet the afore mentioned requirements. Temporal streams are a common abstraction of data streams and data- base relations; the operators of TSA are generalizations of the usual operators of Relational Algebra. A in-depth 'analysis of temporal relations guarantees that valid TSA expressions are non-blocking, i. e. can be evaluated incrementally. In this respect TSA differs significantly from previous algebraic approaches which use specialized operators to prevent blocking expressions on a "syntactical" level

Ubiquitous Nature of Event-Driven Approaches: A Retrospective View

This paper retrospectively analyzes the progress of event-based capability and their applicability in various domains. 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 and hence the paradigm is apposite. In this paper, we briefly overview the development of the ECA (or event-condition-action) paradigm. We briefly discuss the evolution of the ECA paradigm (or active capability) in relational and Object-oriented systems. We then describe several diverse applications where the ECA paradigm has been used effectively. The applications range from customized monitoring of web pages to specification and enforcement of access control policies using RBAC (role-based access control). The multitude of applications clearly demonstrate the ubiquitous nature of event-based approaches to problems that were not envisioned as the ones where the active capability would be applicable. Finally, we indicate some future trends that can benefit from the ECA paradigm

Про один підхід до побудови архітектури розподіленої обробки даних в Інтранет-системах управління технологічними процесами

Запропоновано один з можливих підходів до забезпечення ефективної обробки даних в складних, тобто багаторівневих і розподілених Інтранет-базованих інформаційно-управляючих системах. З урахуванням нових чинників, важливих при створенні таких систем, головна увага приділяється двом взаємопов’язаним проблемам: концептуальному моделюванню даних і процедурам їх інтелектуальної обробки із застосуванням механізму активних правил.Предложен один из возможных подходов к обеспечению эффективной обработки данных в сложных, т.е. многоуровневых и распределенных, Интранет-базированных информационно-управляющих системах. С учетом новых факторов, которые важны при разработке таких систем, главное внимание уделяется двум взаимосвязанным проблемам: концептуальному моделированию данных и процедурам их интеллектуальной обработки с использованием механизма активных правил.One possible approach to providing complex, i.e. multi-level and distributed, Intranet-based information management systems with efficient data processing is proposed. Taking into account some new factors to be important for designing such systems, the principal attention is paid to two interconnected problems: conceptual data modeling and intelligent data processing based on active rules mechanism