SUPPORTING COMMAND REUSE: EMPIRICAL FOUNDATIONS AND PRINCIPLES

Abstract

Current user interfaces fail to support some work habits that people naturally adopt when interacting with general-purpose computer environments. In particular, users frequently and persistently repeat their activities (e.g. command line entries, menu selections, navigating paths), but computers do little to help them to review and re-execute earlier ones. At most, systems provide ad hoc history mechanisms founded on the premise that the last few inputs form a reasonable selection of candidates for re-use. This paper provides theoretical and empirical foundations for the design of a reuse facility that helps people to recall, modify and re-submit their previous activities to computers. It abstracts several striking characteristics of repetitious behaviour by studying traces of user activities. It presents a general model of interaction called "recurrent systems". Particular attention is paid to the repetition of command lines given a sequential history list of previous ones, and this distribution can be conditioned in several ways to enhance predictive power. Reformulated as empirically-based general principles, the model provides design guidelines for history systems specifically and modern user interfaces generally.