ANSWER

User-Centered Design (UCD) is an application design methodology which focuses on usability goals, user demographics, real-world environment, tasks, and workflow in the design of an application interface.  During the analysis phase of UCD, two key stages are the User Analysis stage and the Workflow Analysis stage.

As part of the User Analysis stage, the analyst generates personas in order to document realistic examples of specific users of the system or application.  Later during the Workflow Analysis stage, the analyst examines the different goals that a particular persona would try to achieve through use of the application.  A single path, made up of a series of specific steps, taken through the application to achieve a user goal is a scenario. 

Most analysts are familiar with the term use cases.  A use case describes the main path and alternative paths that a user may take through an application to achieve their goal.  A single path selection through a use case traces a use case scenario.  In general, use case scenarios and UCD scenarios are the same.  However, on a more specific level, there are some subtle differences.

1. UCD scenarios are written for a specific persona.  A persona is a more specific case of user than use case actors.  UCD has a concept of User Profiles which more closely aligns with the concept of use case actors.
   
2. UCD scenarios are almost always written in narrative form while use case scenarios can be written as narratives, two-column dialogues, etc.

In the end, thinking of UCD scenarios as being very similar to use case scenarios will help you gain a pretty quick understanding of what they are and how they are used.

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Chris Adams
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