 Activity diagram is basically a flow chart to represent the flow from one activity to another activity.

1. Actions or activity. 2. Start and End States. 3. Transitions. 4. Decision. 5. Forks and Joins. 6. Swim lane.

 An action represents a single step within an activity, that is, one that is not further decomposed within the activity.

 The start and end states let you know where the flow begins and ends.  Each activity diagram must have a start state, which is drawn as a solid dot, to signify where the flow begins.  End states are optional on the diagram  You can have more than one end state on the diagram, but only a single start state. End state Start state

 A transition shows how the flow of control moves from one activity to another.  We can, set limitations on the transition to control when the transition occurs.  This can be done either by using an event condition.

event

 In creating the activity diagram, you might need to model two or more different sequences of actions.

 You can use the Fork Node and the Join Node to describe two or more threads of activities that can execute at the same time.  A fork node is a control node that splits a flow into multiple concurrent flows.  A fork node has one incoming edge and multiple outgoing edges.  A join node is a control node that synchronizes multiple flows.  A join node has multiple incoming edges and one outgoing edge.