A Component- and Message-Based Architectural Style for GUI Software

While a large fraction of application system code is devoted to user interface (UI) functions, support for reuse in this domain has largely been confined to creation of UI toolkits ("widgets"). We present a novel architectural style directed at supporting larger grain reuse andjexible system composition. Moreover, the style supports design of distributed, concurrent, applications. A key aspect of the style is that components are not built with any dependencies on what typically would be considered lower-level components, such as user interface toolkits. Indeed, all components are oblivious to the existence of any components to which notification messages are sent. Asynchronous notification messages and asynchronous request messages are the sole basis for inter-component communication. While our focus has been on applications involving graphical user interfaces, the style has the potential for broader applicability. Several trial applications using the style are described.