Freedombase needs to know the structure of the existing table, so it will derive the structure, and store the derived structure, including data types and multi valued fields. Freedombase achieves this by both working through the dictionary definitions, and by sampling the data in the existing table.

Freedombase can determine which fields are multi valued. However, in addition, Freedombase requires a controlling field for each multi valued field. By default each field is set as the controlling field for itself. After Freedombase has derived the structure of a table, you will need to replace any non controlling field names in the Control Attribute field, with the appropriate controlling field name.