Scenario-based Design
John Carroll

1. Scenarios in interactive systems design

   In the traditional design of computer software and systems there is a key document called a functional specification ...

2. A strange aid to thought

   Where did scenarios come from? And why have they become so pre-eminent in software design. Interestingly, the main historical root emanates from strategic planning, not design studies; perhaps this is the legacy of the new design methods.

3. The solution-first strategy

   Planning and designing are both examples of ill-structured problem solving. In Cognition and thought, Reitman distinguished ill-structured problems from well-structured problems, such as the familiar puzzles investigated in psychological studies of problem-solving, in three ways: In ill-structured problems, the problem is not fully defined; the possible moves are not all given; and the goal is unknown. The indeterminacy of ill-structured problems encourages a solution-first strategy. Thus, designers typically discover the nature of the problem they are solving by designing a solution and analyzing it. In this way, they exploit the concreteness of their own solution proposals to evoke further requirements for analysis -- sections>

4. Scenarios evoke reflection in design

   Designers are intelligent people performing complex and open-ended tasks. They want to reflect on their activities, and they routinely do reflect on their activities. However, people take pride not only in what they know and learn, but in what they can do and in what they actually produce. There is a fundamental tension between thinking and doing: thinking impedes progress in doing, and doing obstructs thinking.

5. Scenarios relax commitment but support progress

   Design analysis is always indeterminate, because design changes the world within which people act and experience. The rapid evolution of spreadsheet software in the 1980s does not indicate a failure in the original requirements analysis for VisiCalc, but rather suggests the extent to which the original spreadsheet programs altered the work situations in which these program were used

6. Scenarios support many needs/purposes

   Every element of a design, every move that a designer makes, has a variety of potential consequences.

7. Scenarios can be abstracted and categorized

   Schvn emphasized the "dilemma" of rigor or relevance throughout the professions. He describes the "high, hard ground" where practitioners can make use of systematic methods and scientific theories, but can only address problems of relatively limited importance to clients or to society. He contrasts this to the "swampy lowland [of] situations ... incapable of technical solution"

8. Scenarios promote work-orientation

   Designers must have constraints; there are just too many things that might be designed. Requirements, if they can be identified, are clearly the best source of constraints because they indicate what sort of design work is needed. But there are many other sources of constraints. The current state of technology development makes some solutions impossible and others irresistibl

9. Zeitgeist or method?