Supporting concurrency, communication and synchronization in human-computer interaction
Ralph D. Hill, Ron Baecker, William A. S. Buxton · 1987
Better user interfaces to interactive computer systems are needed and one of the best ways to develop them is to iteratively implement, test, and redesign. Currently, a major problem in user interface design and development is that this iterative design approach is very expensive. As an attempt to solve this problem, many User Interface Management Systems (UIMSs) have been proposed. These are software systems specifically designed for rapid prototyping of user interfaces. Unfortunately, most of these are too restricted. In particular, no UIMS that has been reported in the literature is designed to support interfaces where the user is free to use both hands concurrently, for example, positioning an object with one hand while selecting a colour for it with the other. Also, most are severely restricted by a lack of support for communication among various components of the interactive system at run-time. This limits the use of context dependent defaults and error recovery, resulting in inferior user interfaces or increased complexity in the user implementation. This thesis makes two major contributions that address these problems: (1) a new language for specifying the syntax of human-computer dialogue languages, and (2) a new way of supporting communication among the run-time components of a user interface. The syntax specification language is based on a novel language specification technique called Event Response Systems (ERS). These use the paradigm of specifying responses to events, to handle the problems of specifying concurrent dialogues on a small scale. The communications mechanism, called Local Event Broadcast Method (LEBM), is also novel. It addresses concurrency on a larger scale and provides communication support via a simple broadcast method. To show the effectiveness of these ideas, a prototype UIMS, called Sassafras, has been developed. Sassafras has been used to implement a variety of user interfaces, from a very simple keyboard interface, to elaborate direct manipulation interfaces that encourage the use of multiple input devices simultaneously. These illustrate important features of Sassafras that are not found in existing UIMSs.