Activity diagram
The Activity Diagram
 What is it ?
 graphical representation of process and control flow
 Purpose
 Describe business processes and individual use case
scenarios
 Model concurrent behavior
The Activity Diagram (contd.)
 Helpful for modeling workflow and use case scenarios
without having to dive into OO technology.
 Very well understood without any computer knowledge,
so are an excellent means for user communication
 They are also very good means to describe concurrent
behavior in a process.
The Activity Diagram Notation (1)
A Sequence in an Activity Diagram
Synchronization in an Activity Diagram
Parallel Split in an Activity Diagram
Exclusive Choice in an Activity Diagram
Elements of an Activity Diagram
 Registration example
Activity
Start
Browse Course
Catalog
Select Course
Info
Guard
Confirm
Registration
Enter Personal
Data
Branch
[data correct]
End
[else]
Update Course
Kropp, M. SWEED 2001
Send Email
Print Bill
Elements of an Activity Diagram
Customer
Browse Course
Catalog
Registration
System
Select Course
Info
Database
System
Billing
System
Swimlane
[else]
Enter Personal
Data
[data correct]
Confirm
Registration
Fork
Send Email
Join
Kropp, M. SWEED 2001
Update Course
Print Bill
Elements of An Activity Diagram (Contd.)
 The above diagram shows the sequence of steps with




explicit modeling of parallel behavior represented by fork
and join .
fork has one incoming transition and several outgoing
transitions.
The outgoing transitions are all executed in parallel.
join has several incoming transitions and only one
outgoing transition. It is also called a synchronization,
since the join specifies, that the outgoing transition is
only executed when all incoming transitions have
completed their activity.
Swimlanes allow you to specify who is doing a specified
action. For this you arrange your actions in vertical zones,
each separated by dashed lines.
When to Use Activity Diagrams
There are actually two main strengths to activity
diagrams:
1. They can be used very well for visualizing business and
workflow processes. They are not yet SW related and
can be easily understood by users and customers.
2. The support modeling parallel behavior. This again
makes them a very good tool for workflow modeling.
Hence, they can be used for :
 Analyzing Use Cases
 Understanding Workflows
 Describing complicated sequential algorithms
 Modeling parallel behavior
Elements
of
Activity
Diagrams
 Activity: a behavior that an object carries out while in a
particular state
 Transition: a movement from one activity or state to
another
 Branch: a diamond symbol containing a condition
whose results provide transitions to different paths of
activities
 Synchronization bar: horizontal or vertical bars
denoting parallel or concurrent paths of activities
 Fork: the beginning of parallel activities
 Join: the end of parallel activities
 Swimlanes: columns representing different
organizatonal units of the system
branch
activity
synchronization bar
swimlane