Scenarios are descriptions of situations in which a user might go to a knowledge management system. She usually answers questions about Lotus WordPro but receives an occasional question about Microsoft Word. Because she supports the product infrequently, she consults the knowledge base on this product whenever answering questions about it. Developing scenarios does not preclude designers from performing a task analysis. Doing so actually assists with task analysis.
Many task analyses merely describe what users do.
Scenarios add who, why and how to the picture. In some instances, the choice pertains to goal. For example, a user might consult a quick reference instead of a tutorial when the person needs an answer quickly and is not interested in developing competence. In some instances, the choice pertains to role. An executive and a technical expert reading the same report often look for different things.