On an activity diagram, which of the following is NOT a valid use of a synchronization bar?

An activity diagram in UML is a type of flowchart that represents workflows or processes. A synchronization bar, also known as a fork or join node, is used to depict concurrent activities.

Here are some uses of a synchronization bar:

1. To represent the start of concurrent activities (Fork): When a single flow of control splits into multiple concurrent flows, a synchronization bar is used. This is called a fork.

2. To represent the end of concurrent activities (Join): When multiple concurrent flows of control merge into a single flow, a synchronization bar is used. This is called a join.

3. To represent both the start and end of concurrent activities: A synchronization bar can also be used to both split a single flow into multiple concurrent flows and then merge them back into a single flow.

However, the following is NOT a valid use of a synchronization bar:

• To represent decision-making or branching: A synchronization bar is not used to represent decision points where the flow of control branches based on certain conditions. This is represented by a decision node or a diamond shape in the activity diagram. Using a synchronization bar for this purpose would be incorrect as it is meant for concurrent activities, not for decision-making or branching.