...
CatalogueItems can be tied to the underlying database via ExtractionInformation . This means that you can have multiple extraction transforms from the same underlying ColumnInfo e.g. PatientDateOfBirth / PatientYearOfBirth (each with different governance categories).
...
CohortAggregateContainer
Cohort identification is achieved by identifying Sets of patients and performing set operations on them e.g. you might identify "all patients who have been prescribed Diazepam" and then EXCEPT "patients who have been prescribed Diazepam before 2000". This is gives you DISTINCT patients who were FIRST prescribed Diazepam AFTER 2000.
...