1. Activity Diagrams

2. What is Activity Diagrams?  Activity diagrams are a technique to describe procedural logic, business process, and work flow.  An individual activity may be manual or automated and often represents the actions needed to move an object between states.

3. Elements of an Activity Diagrams  Initial node: The filled in circle is the starting point of the diagram. An initial node isn ’ t required although it does make it significantly easier to read the diagram. Symbol:  Activity final node: The filled circle with a border is the ending point. An activity diagram can have zero or more activity final nodes. Symbol:

4. Elements of an Activity Diagrams  Activity The rounded rectangles represent activities that occur. An activity may be physical, such as Inspect Forms, or electronic, such as Display Create Student Screen.

5. Elements of an Activity Diagrams  Parallel Activities:  Fork A black bar with one flow going into it and several leaving it. This denotes the beginning of parallel activity. Symbol:  Join A black bar with several flows entering it and one leaving it. This denotes the end of parallel processing. Symbol:

6. Elements of an Activity Diagrams  Branch: Also called decision. a diamond with one flow entering and several leaving. The flows leaving include conditions although some modelers will not indicate the conditions if it is obvious.  Guard Condition: Text such as [Incorrect Form] on a flow, defining a guard which must evaluate to true in order to traverse the node. Merge: A diamond with several flows entering and one leaving. The implication is that all incoming flows must reach this point until processing continues.

7. Elements of an Activity Diagrams  Partition. Also called swimlanes, indicating who/what is performing the activities (either the Applicant, Registrar, or System).

8. Difference between branch/merge and fork/join  Use forks and join to describe parallel algorithms for concurrent programs. The sequence between those concurrent programs is irrelevant. E.g. a salesperson can either fill the order, send the invoice, deliver, and then receive payment; or in other way, he can send the invoice, receive the payment, fill the order, and the deliver.  Use branch/merge where a decision is to be made. E.g. whether an express delivery is requested, if true, delivery it by an express mail; otherwise, use regular one.