UML scenario example

Question

How are scenarios expressed? I think they're linked to use-cases but I'm not sure and I'm seeking some good examples or a document that can serve as a template.

Answer 1

The problem of UML use cases is that you have use case diagrams, but there is nothing concrete about textual specification. When you follow the Unified Process (UP), which is a methodology by creators of UML and uses UML quite much, there is an activity called use case realization, which is about specifying use cases and therefore also the scenarios. For this, you can use any behavioural diagram. Sequence digrams, state machine diagrams, activity diagrams, communications diagrams, collaborations diagrams, communications overview diagram and timing diagram. Diagrams arenice, but sometimes to verbose, often it is easier to use some simple textual use case scenario specification, e.g. look at what Alistair Cockburn promotes. There are however many other ways which got recently popular, mostly as a part of the Behaviour Driven Development (BDD) approach. Those are informal specifications written in natural language having structure, which is supported by various tools, which are able to help you generate acceptance tests for your requirements expressed through the specifications. For more details look for example at the Cucumber or Fitnesse frameworks.

Answer 2

Scenarios sound like UML sequence diagrams to me:

A scenario is a sequence of steps describing an interaction between a user and a system