Use Case Decomposition
This section should break down the Use Cases in order to show their sequencing and constituent steps.
Map the Use cases identified above into sequences of steps (or System Functions) that compose them. Note any System Attributes that will come into play for certain Use Cases.
Use reference numbers to facilitate easy tracing of requirements
Cover deviations from normal usage (E.g. errors cases)
Illustrate (System sequence diagrams, Full Dressed Use Cases, Etc.)