We propose a software toolkit for developing complex web-based user interfaces, incorporating such things as multi-user facilities, virtual environments (VEs), and interface agents. The toolkit is based on a novel software architecture that combines ideas from multi-agent platforms and user interface (UI) architectures.  It provides a distributed shared database with publish-subscribe facilities.  This enables UI components to observe the state and activities of any other components in the system easily.  The system runs in a web-based environment. The toolkit is comprised of several programming and other specification languages, providing a complete suite of systems design languages.  We illustrate the toolkit by means of a couple of examples.
['B.W. van Schooten', 'Anton Nijholt', 'E.M.A.G. van Dijk']
A software toolkit for web-based virtual environments based on a shared database