This paper examines use of scenarios in task analysis of human-computer interaction. Scenario-based task analysis is categorized into inspection methods. It uses scenarios-concrete stories and examples of past use of existing systems as well as future use of potential systems-as basic tool for task analysis. This paper discusses two types of techniques. On one hand, it illustrates scenario exploration technique, in which we iteratively create scenarios and pose 5W+1H and What-if questions. This activity can be done in group sessions with various stakeholders in system design; in this case, it provides various viewpoints in system analysis. On the other hand, it emphasizes claims analysis technique, in which articulation of claims of technology in scenarios (i.e., systematic enumeration of its potential tradeoffs) provides fair analysis on pros and cons of its consequences. These systematic questions, which system might afford, provide the opportunity to do reflection of analyst's past experiences. In order to remove the cost of task analysis with user participation, this paper points out the importance of the early enrolment of potential users in scenario design meeting. The reason is, once analysts obtain users' goal, task and background information working through scenarios with potential users, they can reuse that information for analysts' walkthrough of new or alternative design. In other words, with the information the analysts can role-play potential users in realistic manner. It will reduce cost of every-time assessments by potential users. As task analysis at the present time provides a broader scope, furthermore, this paper discusses the merit of using scenarios in system design and analysis-such as team building and project management.
Keywords: Claim, claim analysis, scenario, scenario-based design, scenario-based task analysis, tradeoff analysis.