Which of the following roles is NOT directly related to domain separation?

The role that is not directly related to domain separation is the system administrator. The system administrator generally has overarching responsibilities across the entire system rather than being confined to particular domains. This role typically includes managing system-wide configurations, overseeing security protocols, and handling backups and updates, which affect all users and data in the system.

In contrast, the other roles listed—domain_expand_scope, domain_admin, and domain_user—are specifically designed to operate within the context of domain separation. Domain_admins focus on managing specific domains, overseeing their particular users and resources. Domain_expand_scope allows for the expansion and manipulation of data or functions within a designated domain, reflecting its relevance to domain separation strategies. Domain_users are those who operate within specific domains and are restricted to the permissions and resources assigned within those boundaries, which is the essence of domain separation.

This differentiation showcases how the system administrator operates outside the confines of any single domain while the other roles are fundamentally tied to the principles and management of domain separation.