A CMDB Administrator wants only the CIs of Principal Classes to appear in CI reference...

Within Data Foundations, “Configuration” includes designing the CMDB data model in a way that supports operational usability—especially for ITSM processes like Incident and Change. One common usability challenge is that CI reference fields (such as the Incident “Configuration item” field) can become cluttered and confusing if they allow selection from every CI class, including highly technical or rarely used classes. To address this, ServiceNow uses the concept of Principal Classes: a curated subset of CI classes that are considered primary for operational selection and reporting.

Principal Classes are designated in the CI Class Manager, because this is where administrators configure and manage CI class behaviors and class-level settings. Defining Principal Classes at the class-management layer ensures that the platform can consistently apply this constraint across CI reference fields and related experiences. This aligns with Data Foundations goals: improving data quality and process outcomes by making it easier for users to select the correct CI, which in turn increases accuracy for assignment, routing, impact analysis, and analytics.

The other options do not fit the responsibility. CMDB Workspace is primarily used for exploring and analyzing CMDB data, not configuring class-level constraints. CMDB Data Manager focuses on governance automation (like lifecycle policies and bulk remediation operations), not CI class designation rules. System Properties may influence global behaviors, but Principal Class designation is a modeling configuration handled through CI class configuration, which is why CI Class Manager is the correct location.