Usability Specifications as Tool in Iterative Development.

This chapter critiques approaches that consist of usability analysis of fully articulated design alternatives and develops an approach based on usability specifications: precise, testable statements of performance goals for typical users carrying out tasks typical of their projected use of the system.

Abstract

Poor usability of contemporary computer systems has impelled a concern with how usability can play a role in the system design process. In this chapter, we criticize approaches that consist of usability analysis of fully articulated design alternatives. Such approaches cannot in principle support the design process that produced the alternative designs in the first place. We develop an approach based on usability specifications: precise, testable statements of performance goals for typical users carrying out tasks typical of their projected use of the system. These in turn must be factored into their behavioral prerequisites, which we call subskills, in order to pinpoint and remedy specific problems in a design. Like functional specifications, the usability specifications and the subskills they imply are viewed as being iteratively elaborated and refined throughout the design process. An extended example from the domain of text editing is presented.