Computation Via Direct Manipulation

Interfaces to complex equipment can often impose severe difficulties for the user. In part, these difficulties are caused by the abstract nature of the interaction that many modern interfaces present to the operator. A new class of interfaces, the direct manipulation interface, appears to offer improvements in ease of use and understandability because the abstraction of the normal interface is replaced with what might be called the model world metaphor, where the user can feel as if the operations are done directly upon the external environment. Research under this contract examined in detail the nature of directness in the use of computer interfaces. The research demonstrates that the concept of directness is a complex one, involving at least four different aspects of the interface, including two gulfs, one for execution and one for evaluation, and two different kinds of mappings semantic mappings and referential distance. The experimental and theoretical work reported under this contract examines the complexities of the differences among interface styles, demonstrates the importance of visibility and sound in the performance of tasks, and presents a new, detailed analysis of the general attributes of cognitive artifacts, including an important new theoretical construct the object-symbol. Keywords Ergonomics, Human factors, Man computer interaction.