|Activity diagrams describe the workflow behavior of a system. |
Activity diagrams help you to describe procedural logic, business process and workflow of the system.
(Activity diagrams are similar to Flowchart diagrams)
Notations:Initial State: The filled in circle is the starting point of the diagram; denotes start of an activity.
Action State(Activity): The rounded rectangles, denotes represent activities that occur.
State: Rectangle; denotes static state.
Decision: A diamond with one flow entering and several leaving; denotes yes/no decision in workflow.
Fork: A black bar with one flow going into it and several leaving it; denotes the beginning of parallel activity.
Join: A black bar with several flows entering it and one leaving it; denotes the end of parallel processing.
Control Flow: Solid arrow line; denotes the workflow direction.
Object Flow: Dotted arrow line; denotes object flow
Signal Send: Denotes sending a signal.
Signal Receive: Denotes receiving a signal.
Final State: The filled circle with a border is the ending point; denotes end of an activity.
Swim lane: Swim lanes divide activities according to objects.
When to use?Analysis phase and design phase to describe workflow and process.
As a UML compliment flowchart.
Who develops it?Domain Experts.
Example:Following example shows patient appointment booking workflow.
Further readings:UML Distilled -- Martine Fowler
The Unified Modeling Language User Guide --Grady Booch , James Rumbaugh , Ivar Jacobson