What does the filled-in circle in node definition and notation represent?

The filled-in circle in node definition and notation represents the start of the flow of a control token. In modeling and diagramming, particularly within the context of business processes and system verification, the filled circle signifies a point where control or data begins to flow into the activity or process. This concept is fundamental in control flow modeling and helps in visualizing how processes are initiated and how control tokens move through the various elements in a system.

Understanding the role of the filled circle enhances comprehension of process dynamics, emphasizing how activities are activated and how tasks or operations are interconnected within a model. This is crucial for defining clear paths within a system and is part of effective model design that allows stakeholders to grasp the sequence and logic flow of activities within a process.