BEST DESTINATION OF INDONESIA: Activity Diagram

Do You Know Activity Diagram ?? ...

According to Whitten, Bentley, and Dittman (2004, p450-454), an activity diagram is a diagram that can be used to graphically depict the flow of a business process, the steps of a use case, or the logic of an object's behavior (methods). Activity diagrams are similar to flowcharts to describe the sequence of activities of the business process flow or a use case, but in contrast to the flowchart in the provision of mechanisms to describe the activities that appear at the same time.

Activity diagrams are graphical representations of workflows of stepwise activities and actionswith support for choice, iteration and concurrency. In the Unified Modeling Language, activity diagrams are intended to model both computational and organisational processes (i.e. workflows). Activity diagrams show the overall flow of control.

Activity diagrams are constructed from a limited number of shapes, connected with arrows. The most important shape types:

· rounded rectangles represent actions;

· diamonds represent decisions;

· bars represent the start (split) or end (join) of concurrent activities;

· a black circle represents the start (initial state) of the workflow;

· an encircled black circle represents the end (final state).

Arrows run from the start towards the end and represent the order in which activities happen.

Hence they can be regarded as a form of flowchart. Typical flowchart techniques lack constructs for expressing concurrencyHowever, the join and split symbols in activity diagrams only resolve this for simple cases; the meaning of the model is not clear when they are arbitrarily combined with decisions or loops

Ø Simple Control Flows

You can show a sequence of actions with branches and loops. For more information about how to use the elements described here, see the Describing Control Flow section of the topic :

Shape	Element	Description and Main Properties
1	Action	A step in the activity, in which the users or software perform some task. The action can start when a token has arrived at all its incoming flows. When it ends, tokens are sent on all the outgoing flows. · Body - Specifies the action in detail. · Language - The language of the expression in Body. · Local Postconditions - Constraints that must be satisfied when execution ends. The goal achieved by the action. · Local Preconditions - Constraints that must be satisfied before execution begins.
2	Control Flow	A connector that shows the flow of control between actions. To interpret the diagram, imagine that a token flows from one action to the next. To create a control flow, use the Connector tool.
3	Initial Node	Indicates the first action or actions in the activity. When the activity starts, a token flows from the initial node.
4	Activity Final Node	An end to the activity. When a token arrives, the activity terminates.
5	Decision Node	A conditional branch in a flow. Has one input and two or more outputs. An incoming token emerges on just one of the outputs.
6	Guard	A condition that specifies whether a token can flow along a connector. Most frequently used on the outgoing flows of a decision node. To set a guard, right-click a flow, click Properties and then set the Guard property.
7	Merge Node	Required to merge flows that were split with a decision node. Has two or more inputs and one output. A token on any input emerges on the output.
8	Comment	Provides additional information about elements to which it is linked.
9	Call Behavior Action	An action that is defined in more detail on another activity diagram. · IsSynchronous - If true, the action waits until the activity terminates. · Behavior - The activity invoked.
(not shown)	Call Operation Action	An action that calls an operation on an instance of a class.
	Activity	The flow of work that is depicted by an activity diagram. To see the properties of an activity, you must select it in UML Model Explorer. · Is Read Only - If true, the activity should not change the state of any object. · Is Single Execution - If true, there is at most one execution of this diagram at a time.
	UML Activity Diagram	The diagram that displays an Activity. To see its properties, click an empty part of the diagram.

Ø Concurrent Flows

You can describe sequences of actions that execute at the same time. For more information, see Drawing Concurrent Flows :

Shape	Element	Description
11	Fork Node	Divides a single flow into concurrent flows. Each incoming token produces a token on each outgoing connector.
12	Join Node	Combines concurrent flows into a single flow. When every incoming flow has a token waiting, a token is produced on the output.
13	Send Signal Action	An action that sends a message or signal to another activity or to a concurrent thread in the same activity. The type and content of the message is implied by the action's title or specified in additional comments. The action can send data in the signal, which can be passed to the action in an object flow or input pin (16).
14	Accept Event Action	An action that waits for a message or signal before the action can continue. The type of message the action can receive is implied by the title or specified in additional comments. If the action has no incoming control flow, it produces a token whenever it receives a message. The action can receive data in the signal, which can be passed on an object flow or output pin (17). · IsUnmarshall - If true, there can be several typed output pins, and data is unmarshalled onto them. If false, all data appears on one pin.