Final answer:
No, in a system sequence diagram, the order of the messages is determined by their position on the diagram, not by numbering.
Step-by-step explanation:
No, in a sequence diagram the order of the messages is not determined by numbering the messages. Instead, the order of the messages is represented by their position on the diagram. The messages are typically shown as arrows or lines, and the ordering is determined by the direction of the arrows or lines.
For example, if a message A is sent before message B, then the arrow or line representing message A will appear before the arrow or line representing message B on the diagram. The numbering of the messages is optional and is used mainly for clarity or to indicate the sequence explicitly when there are multiple parallel messages.