Among the Elements of Definition, which represents a sequence of actions or operations?

The correct answer is Flow Specification, as it is specifically designed to represent a sequence of actions or operations within a system model. Flow Specifications detail how different actions are connected and how they progress over time in a workflow or process, illustrating the dynamic interactions and transitions that occur between various elements in a system.

Understanding Flow Specifications is essential because they help in clarifying the logic of how processes work, including the order in which tasks must be completed and the conditions that affect the flow. This makes them crucial in modeling complex systems where the order and interaction of operations can significantly impact the overall functionality.

The other options, while important concepts in modeling, serve different purposes. A Block is typically used to encapsulate a whole system or a component's structure and behavior, rather than focusing on a sequence of actions. A Value Type defines the characteristics or properties of data but doesn’t express operational sequences or flows. An Actor represents a user or external system interacting with the model but does not depict the actions themselves. Each of these elements plays a vital role in modeling, but when it comes to sequences of actions specifically, Flow Specification is the most appropriate choice.