This paper begins with an examination of the reasons for the computer industry’s current interest in human factors. The author then briefly reviews several human factors issues that have arisen in his use and studies of various interactive systems. The tradeoffs between command language and menu dialogs are discussed and guidelines are presented for response time, display rates, and the wording of system messages. He concludes the section with a discussion of some factors that need to be considered when providing online tutorials and HELP, and when selecting hardware devices. The paper’s attention is then focused on methods and tools for facilitating user involvement in the system design process.
The final section of the chapter presents a detailed analysis of a user interface dialog which the author calls “direct manipulation.” The central principles of direct manipulation are:
the visibility of the object of interest.
rapidly reversible actions whose impact on the objects are immediately apparent, and
the use of physical actions, rather than command syntax, to directly manipulate the objects of interest.
The author cites several examples of interactive systems that incorporate these principles, including Visicalc, Macintosh, video games, and computer-aided design tools. Several beneficial attributes of systems designed using the direct manipulation principles are then presented as goals for future system design. The author describes a cognitive model of user behavior that was developed to further his understanding of how direct manipulation supports these goals. Finally, potential applications of direct manipulation to personal address listing, checkbook maintenance, bibliographic searching, and airline reservations systems are described.
To this reviewer, this chapter actually represents two substantive papers. The first paper, which consists of the first three sections, presents a clear, concise discussion of the need for human factors input in the design of interactive systems, as well as a set of issues and tools that human factors specialists should be aware of in designing a user interface. This part of the paper would serve as an excellent introduction to current human factors work in system design for those who are not human factors practitioners.
Three key points are made by the author in the first three sections of the paper:
Controlled experimentation is needed in investigating human factors issues.
Testing of user interface designs is needed to provide data for making design decisions and modifications.
Users of interactive systems need to be involved in the design of the system.
This reviewer concurs that design decisions and resolutions of human factors issues should be based on data and not on expert judgement or guidelines, when possible. In order to support the testing of interfaces with end users, time must be set aside in the system design lifecycle and rapid prototyping tools must be available.
The second paper, the last section of this chapter, introduces the reader to the concept of direct manipulation and its applicability to interactive system design. This section should be of interest to the experienced system designer looking for innovative approaches to interface design for interactive systems. Research into the concept of direct manipulation will clarify whether and how the benefits stated by the author can be realized in large-scale systems for record keeping and retrieval, reservation tracking, and command and control.
