The Strata of a Data-Field is a description of the nature of the data it describes. There are four categories:
- Primary - the key clinically/scientifically relevant data-fields;
- Derived - data which has been constructed by combining/processing values from one or more other data-fields;
- Supporting - data which is clinical/scientific in nature, but largely superceded by a Primary data-field;
- Auxiliary - data which describes the systems or processes used to acquire the data.