What technique would be best to clarify the boundaries of the system?

Interface analysis is a technique focused on clearly defining the boundaries of a system and identifying how it interacts with other systems or components. This method involves analyzing the points of interaction, data exchange, and operational flow between the system and its environment, which is crucial for understanding what the system will and will not include.

By utilizing interface analysis, stakeholders can establish a clear understanding of the requirements and functionalities that need to be addressed within the system's scope. This clarity helps ensure that all participants in the development process have a common understanding of the system boundaries, which is essential for preventing scope creep and facilitating effective communication.

Other techniques listed, such as closed-ended interviews, brainstorming, and mind-mapping, serve different purposes. For example, closed-ended interviews may be used to gather specific information but may not effectively illustrate the boundaries of a system. Similarly, brainstorming and mind-mapping are useful for exploring ideas and generating concepts but do not specifically target the definition of system boundaries to the same extent that interface analysis does. Therefore, interface analysis stands out as the most effective method for this particular goal.