So, I'm learning various aspects of design and architecture, such as UML and use cases. But I'm not getting what a use case scenario is and I can't find much about it. Can anyone explain them to me?
2 Answers
An entire use case can be represented by one activity definition, comprising elements such as decision nodes and activity usages. A scenario is one particular path through such an activity definition. Imagine printing an activity definition and then using a highlighter to trace through decision diamonds. That’s a scenario.
The scenario isn't necessarily described as an activity diagram. Very often, the scenarios are first identified and described in plaintext, before being formalized in an activity diagram:
A very popular format is Alistair Cockburn's template (see here with some examples). He suggests to start with a main success scenario, then provide alternative scenarios (for slight variations, extensions, as well as the unhappy case such as errors, exceptions, failures). By the way, his book "Writing effective use-cases" is a must-read in the field, even if it's more about use-cases than about UML.
There are many other templates used and sometimes scenarios are called "flow" or "path". They can be presented in a tabular form or in a chronologicaly numbered sequence. Sometimes the tabular description has a column for the actor actions and a column for the system action.
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