Describe the various components in sequence diagrams.

Object lifeline: - It shows the lifetime of an object creation and its destruction. If the object is created or destroyed during the time span the diagram represents, then the lifeline stops or starts at the appropriate point. An object's destruction is marked with a large X.

Activation: - It is a time period during which actor is performing an action.

Lifeline: - The Lifeline says that there exists some condition on the object lifetime.

Message: -The Message shows the communication between objects that conveys information and results in an action.

Message (call):- It is same just like a message but also conveys some information and results in action.

All messages have similar definition as the Message (Call) given above.

2-Element Constraint: - It represents a constraint on two classes or associations.

OR constraint: - It represents an OR constraint on two classes or associations.