The Item Type of a Data-Field describes the type of item which is held. There are three categories:
- Data - data values, of elementary types or with simple structures;
- Samples - inventory information corresponding to biological samples held by UK Biobank;
- Bulk - large complex objects, typically binary files (blobs) which cannot be decomposed into smaller chunks.
- Records - inventory information describing the number of (records) held.
Both Bulk and Records type data are available to researchers only for in-situ use via the secure portal.