We describe enhancements for the standard Corba Event Service, extending support for multimedia data flows, quality-of- service definition, a capability-based security mechanism, and multicast event delivery. The resulting service specification is flexible, efficient, and widely applicable. It provides a useful framework for integrating multimedia content with a standard event-based messaging service. O ur research combines the areas of distributed object technology and multimedia messaging. The com- mon object request broker archi- tecture (Corba) standards provide an open and flexible architecture to solve the problems pre- sented by heterogeneous network components. This article describes enhancements to the stan- dard Corba Event Service (CES) to support the distribution of event messages with multimedia content. We propose the concept of a stream event, an abstraction used to describe an event notification message that encapsulates multime- dia content. Support for reliably distributing and managing stream events occurs by using enhanced interfaces and protocols in the CES. The enhancements and implementation of the CES we describe here are useful to any distributed application that requires event-based multime- dia propagation. Groupware applications 1 often benefit from using an optimized event or messaging service, while multimedia applications use and transport special forms of program data such as images, sound, and audio and video streams. Multimedia applications also usually have special quality-of- service (QoS) requirements because of their isochronous nature. Real-time groupware appli- cations 2 share many of the same requirements and characteristics as multimedia applications. They’re both usually highly interactive, they often require real-time notification of events (possibly generated by other participants), and they may operate in a shared environment such as multiuser virtual reality environments and teleconferencing systems. The research hypothesis that underpinned our work was that future applications would need to exchange multimedia content in the context of asynchronous event notification. This article describes the results of a research project focused on enhancing the standard CES to support this requirement. The evaluation shows that we can implement the enhanced service definition effi- ciently in a Java-based environment, using appropriate multicast protocols and a complex event management algorithm. Corba services Corba specifies a system that provides inter- operability between objects in a heterogeneous, distributed environment and in a way that’s transparent to the programmer. Its design is based on the Object Management Group (OMG) Object Model. 3 This model defines common object semantics for specifying the externally visible characteristics of objects in a standard and imple- mentation-independent way. In this model, clients request services from objects (which are implemented as servers) through a well-defined interface. OMG also specifies a set of Object Services. These services provide generic interfaces and pro- tocols to solve recurring problems faced by dis- tributed application developers—essentially, they’re a collection of services (interfaces and objects) 4 that support basic functions for using and implementing objects. Services are necessary for constructing any distributed application and are always independent of application domains. The OMG specifies them as domain-independent interfaces that might be used by many distrib- uted object programs. For example, the Corba Naming Service dis- covers other available services, and it’s almost always necessary, regardless of the application domain. The most relevant Corba-defined ser- vices for our research are the Event Service 5 and the Audio/Video Streaming Service. 6 The latter specifies how to create and manage audio and video data streams within a Corba framework. 56 1070-986X/02/$17.00 © 2002 IEEE A Multimedia Enhanced Distributed Object Event Service Desmond Chambers, Gerard Lyons, and Jim Duggan National University of Ireland Feature Article