Which option best describes how enrollment history can be preserved in the model?

• A. TRIAL with versioning
• B. PATIENT with birthdate
• C. ENROLLMENT with valid_from and valid_to
• D. SITE with address changes

Answer: (C)

Capturing enrollment history hinges on recording the time window during which an enrollment is active. By attaching valid_from and valid_to to each enrollment record, you explicitly store when that enrollment starts and ends, or that it is ongoing. This lets you reconstruct the exact enrollment state for any given date, support historical queries, and audit changes over time. It’s a straightforward, standard way to model time-varying relationships: you can ask who was enrolled at a site on a specific date, how enrollments moved from one site to another, and when those changes occurred.

The other options don’t fit this goal as directly. A TRIAL with versioning tracks changes to trial definitions, not patient enrollment histories. A PATIENT record with birthdate doesn’t describe enrollment periods. A SITE with address changes updates site details, not the temporal enrollment of patients.