Task: Decompose Activity Diagrams

This task refines the black-box activity diagram that describes the use case functional flow.

Purpose

To group functional requirements into actions and show how these actions are logically linked together by decomposing the black-box activity diagram.

Relationships

Roles	Primary: Requirements Engineer	Additional:	Assisting:
Inputs	Mandatory: System Use Case System Use-Case Internal Block Diagram	Optional: System Use-Case Activity Diagram System-Wide Requirements	External: None
Outputs	System Use-Case Activity Diagram

Main Description

There are two general rules to follow when you perform this task:

Don't go too deep with the decomposition: the recommendation is no more than two levels below the top level
Homogeneously decompose across all activities

Steps

Perform a functional decomposition of the coarse-grained system functions

For each high-level system function identified, determine what the system must do to provide the required functions. Replace the top-level action nodes with actions representing each of the leaf functions.

Determine the sequencing of functions required

Create control flows to sequence the system functions (actions) to generate the required behavior.

More Information

Guidelines	Creating an Activity Diagram Logical Decomposition of a Use Case Black-Box Activity Diagram