Which process model notation relies heavily upon logical operators called "rules"?

The process model notation that relies heavily upon logical operators called "rules" is the Event-driven process chain (EPC). This notation is specifically designed for modeling business processes by employing events that trigger functions and connecting them through logical connectors, which represent rules for the flow of the process. This characteristic allows EPCs to effectively depict complex decision-making pathways within a business process by using these logical operators to define how processes should be executed based on specific events.

Event-driven process chains are particularly useful in illustrating both the flow of activities and the decision points that guide the progression through various routes of a process, effectively demonstrating how certain conditions lead to certain actions. This distinction sets EPC apart from the other notations listed, as they do not emphasize the use of logical rules to the same extent.

Flow Charts provide a basic representation of processes without the depth of decision-making provided by rules. Unified Modeling Language (UML) is more focused on software systems rather than purely business processes, making it less applicable in this context. Value Stream Mapping is primarily concerned with identifying and improving the flow of materials and information in a production process, again differing from a rules-based approach. Therefore, the unique reliance on logical operators as rules in EPC makes it the correct answer for this question