Designing time at the user interface: a study of temporal aspects of usability

This thesis is concerned with temporal factors from the perspective of the interactive designer/interface designer and usability as a construct for guiding design activity. The research reported herein examines the many factors which emerge when considering the name of interaction at the user interface. Temporal Aspects of Usability (TAU) is presented as a multivariate construct. It is neither a property that exists 'in the head alone' not is it an aspect of the system but rather an emergent property arising from task based interactions. From a theoretical perspective, it is argued that the inclusion of temporal considerations to the task model more fully specifies 'Usability' as a design construct. A model of TAU is evolved and validated utilizing situated interviews with designers. This resulted in an Enhanced model of TAU. A method for developing temporally informed task models, KAT-LITTER (Leveraging Interactions Through Effective Responses), provides temporal design heuristics as the confluence of, KAT (Knowledge Analysis of Task) a task analysis method, and the enhanced TAU model. As a method, KAT-LITTER is device independent, data centered, domain specific and necessarily independent of existing implementations. A process evaluation of KAT-LITTER showed that it influenced the design process in two significant ways: firstly, designers using KAT-LITTER spent more time reasoning about temporal issues than designers using KAT alone, and secondly these same designers considered a broader spectrum of temporal issues. The development of TAU, its accompanying method, KAT-LITTER, complete with a notational system for analysis represent a significant step forward.