Design and evaluation of a wide-area event notification service

Abstract

The components of a loosely coupled system are typically designed to operate by generating and responding to asynchronous events. An event notification service is an application-independent infrastructure that supports the construction of event-based systems, whereby generators of events publish event notifications to the infrastructure and consumers of events subscribe with the infrastructure to receive relevant notifications. The two primary services that should be provided to components by the infrastructure are notification selection (i.e., determining which notifications match which subscriptions) and notification delivery (i.e., routing matching notifications from publishers to subscribers). Numerous event notification services have been developed for local-area networks, generally based on a centralized server to select and deliver event notifications. Therefore, they suffer from an inherent inability to scale to wide-area networks, such as the Internet, where the number and physical distribution of the service's clients can quickly overwhelm a centralized solution. The critical challenge in the setting of a wide-area network is to maximize the expressiveness in the selection mechanism without sacrificing scalability in the delivery mechanism. This paper presents SIENA, an event notification service that we have designed and implemented to exhibit both expressiveness and scalability. We describe the service's interface to applications, the algorithms used by networks of servers to select and deliver event notifications, and the strategies used • 333 to optimize performance. We also present results of simulation studies that examine the scalability and performance of the service.

Automated context dissemination for autonomic collaborative networks through semantic subscription filter generation

“…It is an extension of content based networking (CBN) [21], which involves the forwarding of events across a network based on subscription filters based on the (meta-)data of the event's contents. KBN extends this and states that the semantics of messages play an important part in the matching of publications to subscriptions.…”

“…To this end, the Sienna publish-subscribe system, originally devised for CBN, was extended with more expressive semantics for the specification of subscription filters [22] to satisfy the KBN vision. Carzaniga et al [21] additionally propose a set of efficient and scalable routing strategies to forward messages from publishers to interested subscribers. The KBN extension [22], proposed by Keeney et al, adds limited support for semantic messages and filters.…”

Reasoning about asynchronous behaviour in distributed systems

“…In Enterprise Application Integration we will have many different applications running and exchanging messages [2,3,9]. Each will have a set of goals which it is trying to achieve.…”

A Novel Approach to Context-Aware Content-Based Middleware

“…SilboPS, our implementation of content-based publish/subscribe inspired by SIENA [11,9], solves this problem by adding two new elements to the paradigm: the context and the context function. Context represents the actual contextual information specific to the message to be sent or that needs to be notified to the subscriber, whereas the context function is evaluated using the publisher's context and the subscriber's context to decide whether the current message and context are useful for the subscriber.…”

“…A communication middleware that supports context decidedly eases application development in pervasive computing. However, the use of context should not be mandatory; otherwise, the communication middleware would be reduced to a context middleware and no longer be compatible with non-context-aware applications.SilboPS, our implementation of content-based publish/subscribe inspired by SIENA [11,9], solves this problem by adding two new elements to the paradigm: the context and the context function. Context represents the actual contextual information specific to the message to be sent or that needs to be notified to the subscriber, whereas the context function is evaluated using the publisher's context and the subscriber's context to decide whether the current message and context are useful for the subscriber.…”