A data architect needs to create an app to analyze 30-day re-admissions at a hospital.

• The medical record system does NOT calculate re-admission data

• The business rule to follow: if a patient is admitted to a hospital within 30 days after being discharged from a previous hospital stay, that event should be captured in the app with a flag called "30-day Re-admission"

• Data being used from the patient record includes hospital account ID, patient ID, admission dater and discharge date

Which action should the data architect perform first to meet these requirements?