| History tools allow users to have access to past interactions kept in a history and to incorporate them into into the context of their current operations. Such tools appear in various forms in many of today's computing systems, but despite their prevalence, they have received little attention as user support tools. This dissertation investigates, through a series of studies, the prospects for history based, user support tools. The studies focus on three primary factors influencing the utility of history-based, user support tools: design of history tools, support of behavioural phenomena in user interactions, and mental and physical effort associated with using history tools.;In surveying a wide collection of history tools, we identified seven independent uses of the history information. However, no single history tool supports all seven uses. Therefore, we propose several kinds of history information and history functions, based on cognitive and behavioural considerations, that need to be supported in new designs of history tools integrating all seven uses of history.;In an exploratory study of the U scNIX environment, we found that users repeated the interactions over the course of a session. Borrowing two concepts and techniques from computer memory research (i.e., working sets and locality), we examine this repetition behaviour and elated strategies for predicting repetitive opportunities and candidates.;Finally, the effort, mental and physical, associated with using a history tool to expedite repetitive commands can influence a user's decision to use history tools. Using the MHP/GOMS cognitive modelling framework, we analyze the human-information-processing operations involved in a history task and in a typing task.;The results of the three sets of studies provide insights into current history tools and they point favourably towards the use of history tools for user support, especially history tools that support the reuse of previous commands. Our studies demonstrate the importance of considering various psychological and behavioural factors and the importance of different grains of analysis. |
