A common notification service

CORBA is a promising software platform for CSCW applications. However, the current CORBA ORBs only provide low-level services. Building CSCW applications is still a complex task. In this paper, we discuss how a common notification service can be added to the CORBA architecture to deal with common user interface events in a distributed environment. This notification service is based on the already standardized Event Service and is design to support awareness in distributed environments. 1. Why using CORBA as a CSCW platform? The construction of CSCW applications has been a difficult task. One of the reasons is that CSCW applications usually comprise of a set of modules that must be integrated: user interface management, distribution package, database and so on. In the development of earlier CSCW systems, the integration of these basic modules must be done by the application programmers, which made it difficult for them to focus on the applications themselves. The adoption of CORBA releases this burden from the application programmers, which makes it possible to extend both the range and the scale for CSCW applications. More specifically, CORBA offers the following advantages for CSCW application development: • Distribution support The distribution support provided by ORB packages can be directly used to implement synchronous communication in many CSCW applications such as shared editors and conferencing tools. • Interface Definition Language The Interface Definition Language (IDL) as part of the CORBA specification makes it easier to integrate software modules implemented in different programming languages. • Distributing existing systems It is very likely that most of the future CSCW applications will be built on top of the current software systems such as word processors, drawing editors, CAD/CAM and so on. One of the reasons is that these systems may already have a large user base. These users, as it has been shown in several occasions in software history, are reluctant to move over to a totally different system simply because it provides CSCW functionality. Therefore the technology to bring existing non-distributed systems into the CSCW arena is critical for making CSCW applications accessible to large user groups. In this respect, CORBA provides some very interesting support due to its IDL and architecture for distribution transparency. • Integration into large software environment Even though computer network will be less expensive and easily available in the future, both personal and enterprise software environments will contain software components other than those dedicated for collaboration tasks. People will spend much of their time writing their individual reports, personal letters, and other tasks that do not require collaboration with others. CSCW software is therefore only a part of the entire software environment used by an individual or an enterprise. However, when people want to collaborate with others, they should be able to do so without any technical difficulty. Thus, CSCW software should be integrated into the total software environment. In this respect, CORBA provides an interesting software platform for building software environments that allow different software components written in different languages to be integrated. 2. Rapid application development Although CORBA in the long run seems to be a very promising software platform for CSCW development, current CORBA packages do not provide sufficient support for rapid development of CSCW applications. This is because most of the services provided by CORBA packages, including Naming Service, Lifecycle Service, Event Service, Persistent Object Service, are low-level services. These services are essential for CSCW