What initiates the flow of events in a use case?

The flow of events in a use case typically begins with an action taken by a primary actor. This is because in systems analysis, a primary actor is defined as an individual or entity that interacts with the system to achieve a specific goal. The initial action they perform triggers the sequence of events that make up the use case, guiding the system through various scenarios.

When the primary actor takes an action, it can be anything from logging into a system, submitting a form, or requesting a service. This action provides the context for the use case and ensures that the flow is aligned with the user's intentions and needs. The use case is designed to capture how the system responds to these initial inputs and to outline the responses involved until the goal is achieved or the process is completed.

The other choices do not fit the definition of how a use case is intended to operate. A random user interaction lacks a specific goal or context, which is crucial for initiating a use case. A system-generated notification, while important in various scenarios, does not stem from a primary actor's intent and is typically a response rather than an initiation. A time-triggered event may be relevant in certain use cases, such as scheduled tasks or alerts, but it is not the most common starting point