Which of the following is NOT a type of model element found in a Package Diagram?

In a Package Diagram, certain model elements are utilized to visually represent and organize components of a system. Actors, Value Types, and Flow Specifications are all integral elements commonly found in these diagrams.

Actors represent the roles that external entities play in the system, providing insight into interactions between users and the system. Value Types help define the types of data that are manipulated within the system, offering clarity on the data flows and structure. Flow Specifications denote the particulars of how information or control flows between different parts of the system, contributing to the understanding of system dynamics.

Event Triggers, on the other hand, are not typically represented as modeling elements in Package Diagrams. They are more closely associated with behavior diagrams such as State Machine Diagrams or Activity Diagrams, where they serve to indicate conditions that cause transitions between states or activities. The absence of Event Triggers from Package Diagrams makes it clear that they do not belong within the context of organizing and depicting the modular structure and relationships of packages within a system.