When an artifact comes from a specific dug area, excavationUnitId records which ExcavationUnit it belongs to. This field is optional — some finds (for example surface collections) are not tied to a unit. When set, it places the artifact within a unit's vertical and horizontal context alongside the unit's stratigraphic layers. If the parent unit is later deleted, the link is cleared rather than deleting the artifact, so the catalog record survives.
Technical section
Data model, API, and internals — visible to developers.