ConcurTaskTrees: An Engineered Notation for Task Models

Task models represent the intersection between user interface design and more engineering approaches by providing designers with a means of representing and manipulating a formal abstraction of activities that should be performed to reach user goals. For this purpose they need to be represented with notations able to capture all the relevant aspects. In this paper the ConcurTaskTrees notation is described and discussed with particular attention to recent evolutions stimulated by experiences with its use and the need to address new challenges.