Subject: Object Oriented Modeling and Design

Difficulty: Medium

Marks: 4 Marks

Structured control in sequence diagram: It defines statements or group of statements in a diagram which determines the sequence of execution of other instructions or statements.

Conditional execution:

1. In sequence diagram conditional statements are used to check the condition.
2. Alt operator is used to indicate the condition in sequence diagram. The body of the control operator is divided into multiple sub regions by horizontal dashed lines.
3. Each sub region represents one branch of a condition. Each sub region has a guard condition. If the guard condition for a sub region is true, then that sub region is executed.
4. At most one sub region may be executed.
5. One sub region may have the special guard condition [else]. This sub region is executed if none of the other guard conditions are true.

Example

In the above example alt operator is used to show condition as amount >=balance. If the condition is true then, update operation will be perform on account object.If the condition is false then, else region executes if a message as insufficient funds from account object to bank object