The publish/subscribe (or pub/sub) paradigm is an increasingly popular model for interconnecting applications in a distributed environment. Many existing pub/sub systems are based on pre-defined subjects, and hence are able to exploit multicast technologies to provide scalability and availability. An emerging alternative to subject-based systems, known as content-based systems, allow information consumers to request events based on the content of published events. This model is considerably more flexible than subject-based pub/sub. However, it was previously not known how to efficiently multicast published events to interested content-based subscribers within a large and geographically distributed network of broker (or router) machines. We develop and evaluate a novel and efficient distributed algorithm for this purpose, called -link matching". Link matching performs just enough computation at each node to determine the subset of links to which an event should be forwarded. We show via simulations that: link matching yields higher throughput than flooding when subscriptions are selective; and the overall CPU utilization of link matching is comparable to that of centralized matching.

Msting GUI btider technology supports btiding user interfaces for interactive applications via direct manip ulation.However, it is notoriously ~ctit to btid the underlying data sharing and application logic for rmdti-user synchronous co~aborative applications.This paper describes a co~ection of very high-levd software components, bfit using the JavaBeans component standard, that enables domain experts and application dsigners to rapi~y bfid entire co~aborative apphcatiorts via Visual progr arnming -drag-and~op, customization and wiring.Our component suite supports conference setup, awareness, data sharing, media streaming, acc~s synchronization, and tempordy coordinated media and event streams.TVe ~nstrate that the task of btiding non-trivia mdti-user applications using this approach is si@-tly s"np~ed. Ke~ordsRapid Application Devdopment, Visud"Rogramming, Software Components, Java Beans, ~en&Server Synchronous CoUaboration ~TRODUCTIONAs the use of distributed applications is becoming more widespread in today's networked world, the relevance of synchronous collaboration is sharply increasing.Users in a number of application domains are seeking syn-&onous co~aboration ~pabiities within their appfi-cation~.The requirements of this broad range of a~ p~cations me diverse enough that a 'one size fits d" approach to b@ding applications is no longer satisfactory.Our qerience suggests that rapid turnaround of customized co~aborative applications is critid to meet this incressed demand for synchronous co~aboration.Permission to make di~tal or hard copies of d] or part ofthis \\-orkfor personal or cl~aom use is granted without fee protided that copies are not made or dis~%uted for profit or commercial adv-antageand that copies bar this notice and tie fill citation on tie fmt paga To copy orhmlisa to Tepubtish.topost on swera or to rdlsmiute to ~sts, rquires prior ~etific permission and!or a f= CS~V 98 Sattle Ii'zshington GSA Cop~fight AChI 199S 1-5S1134094/9S/1 1...S5.00 . .

The paper presents our state sharing support for building object oriented interactive groupware in wide area distributed environments. We motivate and present an asynchronous model for updating replicated state, which supports atomicity of updates across multiple shared objects. Coupled with our flexible marshalling framework, this model allows existing application data structure classes to be easily extended and made shareable. To solve the problem of replica consistency we use a novel combination of three mechanisms: (1) global locks, (2) detection of incorrect update ordering, and (3) cloning a subset of the shared objects and state reinitialization. Finally, to reduce network load due to fine grain user interaction, we provide a framework for application specified event batching called Late Event Modification.