THE OBJECT-ORIENTED DESIGN WORKFLOWActivity Diagrams

The Activity Diagram

Activity diagrams are sometimes called “object-oriented flowcharts”. They allow you to model a process as a collection of activities and transitions between those activities.

Activity diagrams are used to document workflows in a system, from the business level down to the operational level.

The general purpose of activity diagrams is to focus on flows driven by internal processing versus external events.

Guidelines for Building Activity Diagrams

Since the activity diagram can be used to model any kind of process, you should first set the context or scope of the activity being modeled. Once you have determined the scope, you should give the diagram an appropriate title.

You must identify the activities, control flows, and object flows that occur between the activities.

You should identify any decisions that are part of the process being modeled.

You should attempt to identify any prospects for parallelism in the process.

Some other things to keep in mind…

Limit the diagram to a single node that starts the process to be modeled and one final-activity node.

When modeling high-level business processes or workflows, you should only include the most important decisions. Make sure that the guard conditions associated with the outflows of decisions are mutually exclusive (i.e., all potential values of a decision are associated with one of the flows).

When decision modeling, you should only include forks and joins to represent the more important parallel activities in the process.

You should lay out the activities on the diagram in a left to right and/or top to bottom order based on the order that the activities are executed.

Swimlanes should only be used to simplify the understanding of the diagram and you should not have more than five lanes.

Finally, you should challenge any activity that does not have any outflows or any inflows. Activities with no outflows are referred to as black-hole activities. An activity that does not have any inflow is known as a miracle activity.

The Activity Diagram

BankATM MachineCustomer

Activity DiagramWithdraw Use Case Scenario

Insert Card

Enter PIN

Enter Amount

Take Money from Slot

Authorize

[valid PIN] [Invalid PIN]

Check Account Balance

Debit Account

[balance >= amount]][balance < amount]

Show Balance

Eject Card

Take Card

Start

Activity

Branch

Fork

Join

Merge

The End!

Swimlane

Completion Transitions

Branching

Forking and Joining

Swimlanes

Modeling a Workflow

Activity Diagram Resources

IBM:– http://www-128.ibm.com/developerworks/rational/library/28

02.html

Agile Modeling:– http://www.agilemodeling.com/artifacts/activityDiagram.ht

m– http://www.agilemodeling.com/style/activityDiagram.htm