Which aspect of interoperability involves maintaining control over who can access data?

The correct answer is focused on the concept of "access control," which refers to the mechanisms and policies employed to determine who can access specific data and under what circumstances. In the context of interoperability, access control is critical for ensuring that sensitive information is only available to authorized users and systems.

This aspect is particularly significant in the Internet of Things (IoT) environment, where multiple devices and services may interconnect and exchange data. Effective access control allows organizations to safeguard their data while enabling interoperability among devices by allowing specific interactions based on permissions.

In the context of the other options, usage pertains to how data is utilized once access is granted, which does not directly relate to the control over who can access it. Discovery involves the ability to locate and identify resources in a network, while data visualization deals with how information is presented and interpreted. Neither of these concepts directly addresses the management of access rights to data, which is the core focus of access control.