Activity Diagrams


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.
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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.
Analysts.
Developers.

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

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