MULTIPLE USES OF SCENARIOS: A Reply to Campbell Richard M. Young and Philip J. Barnard Robert Campbell performs a valuable service to the HCI community in pointing out the several different uses of "scenarios". While the diversity certainly exists, we believe he has mis-analyzed it and missed an important commonality. Although he begins his summary by claiming that "scenario" has four major meanings, the examples in his article in fact demonstrate a number of different purposes and appli[ cations of scenarios - which is surely not something to complain about - drawn from sources which exhibit a significant commonality of meaning. The common core, for us, concerns the role of scenarios in concretisingsomething for the purposes of analysis and communication. This concreteness helps a designer to imagine what a proposed interface will be like from the user's point of view, something which is important but is also hard for designers to do without the help of an appropriate technique (cf. Young, Green & Simon, 1989). Such a concern contrasts with the more common approach to analyzing an interface solely in terms of its characteristics,j~atures, or propertieswhich we would argue is in many cases misleading and unproductive. The concreteness also enables HCIers (designers, analysts, and researchers) to deal with complicated and rich situations and behaviors in their own terms instead of being restricted to dealing with them one issue at a time. Campbell is also mistaken in accusing us of assuming "that HCI scenarios are all the same, and ignoring the art or science that goes into selecting them." The multiple uses of scenarios, and criteria for choosing among them, are dealt with in our original paper (Young & Bamard, 1987). Our more recent work distinguishes between usagescenarios and design scenarios (although both are relevant to HCI design), and the "horses for courses" aspect of scenario selection is analyzed more deeply in a paper presented at the 1991 HCI Conference (Young & Barnard, 1991), which propounds the idea of paradigm tasks and signature tasks in HCI scenarios. We need to correct the impression given by CampbeU, based on just one out of the forty or so cases we have now analyzed, that our use of scenarios is confined to interfaces which "no one would build any more". For example, one of our recent scenarios concerns the provision of an Undo facility for a multi-user (and potentially multimodal) collaborative document editor (Young, 1992), and it is hard to get more trendy than that! (And as a matter of fact, although Campbell claims, with regard to one of the scenarios in our SIGCHI Bulletin article (Young, Barnard, Simon & Whittington, 1989), that "No one is designing line editors any more", it was brought to our attention not long ago that precisely the editor design dealt with in that scenario had been released as the editor on a public email system offered by British Telecom!) Campbell would like to see our version of scenarios described as "test cases". The limitation of that suggestion is its focus on the role of scenarios for probing the validity of different approaches to HCI, whereas we went to some pains to stress their relevance to the question of scope (Young & Barnard, 1987) and their contribution to communication and integration (Young et al, 1989; Hammond, 1991). We are sympathetic to Campbell's aims. We wish him luck in his enterprise of trying to reform the terminology, but suspect that he may be tilting at windmills. We would not rate highly his chances of succeeding in changing the community's use of the term "scenario", just as we would regard it as utterly quixotic to try to legislate the (even more confused and confusing) usages of terms such as "mental model" or even "model".

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