Realizing Use Cases

• A use case is realized in a collaboration. A collaboration is an implementation of a use case in terms of classes/objects and their relationships called its context. The interactions in the collaboration achieve the functionality of the use case.
• A collaboration is represented as a number of diagrams showing its context and interactions between them. The context is made up of classes. The interactions are the collaboration diagrams, sequence diagrams, and activity diagrams.
• A scenario is an instance of a use case or a collaboration. The scenario is a specific execution path (a specific flow of events) that represents a specific instantiation of the use case. Its external behaviour is an instance of the use case. Its internal representation is the collaboration between the implementing classes/objects and their interactions.