Which statement best distinguishes object flow from control flow?

Which statement best distinguishes object flow from control flow?

• A. Object flow transports object tokens, while control flow transports control tokens.
• B. Object flow transports data; control flow transports signals.
• C. Object flow is optional; control flow is mandatory.
• D. Both depict the same thing and are interchangeable.

Answer: (A)

In UML Activity Diagrams, there are two kinds of flow edges: control flow and object flow. The key idea is what they carry and how they guide execution. Control flow carries control tokens that determine the order in which actions occur, basically signaling the next step to start. Object flow carries object tokens, which represent data or objects moving from one action to the next. Because of this distinction, the statement that best distinguishes them is that object flow transports object tokens while control flow transports control tokens. This captures the fundamental difference: sequencing versus data movement. The other ideas mix up what is carried—data versus signals—and overlook that control flow is about ordering, not signals, while object flow is about passing data. For example, finishing a step might pass a data object along an object flow to the next step, whereas the control flow ensures that the next step doesn’t begin until the current one completes.

In UML Activity Diagrams, there are two kinds of flow edges: control flow and object flow. The key idea is what they carry and how they guide execution. Control flow carries control tokens that determine the order in which actions occur, basically signaling the next step to start. Object flow carries object tokens, which represent data or objects moving from one action to the next. Because of this distinction, the statement that best distinguishes them is that object flow transports object tokens while control flow transports control tokens. This captures the fundamental difference: sequencing versus data movement. The other ideas mix up what is carried—data versus signals—and overlook that control flow is about ordering, not signals, while object flow is about passing data. For example, finishing a step might pass a data object along an object flow to the next step, whereas the control flow ensures that the next step doesn’t begin until the current one completes.