An empirical methodology for writing user-friendly natural language computer applications

A six-step, iterative, empirical, human factors design methodology was used to develop CAL, a natural language computer application to help computer-naive business professionals manage their personal calendars. Language is processed by a simple, non-parsing algorithm having limited storage requirements and a quick response time. CAL allows unconstrained English inputs from users with no training (except for a 5 minute introduction to the keyboard and display) and no manual (except for a two-page overview of the system). In a controlled test of performance, CAL correctly responded to between 86% and 97% of the inputs it received, according to various criteria. This research demonstrates that the methodological tools of the engineering psychologist can help build user-friendly software that accommodates the unruly language of computer-naive, first-time users by eliciting the cooperation of such users as partners in an iterative, empirical development process.