The control type (which can be None if all the required controls have already been defined in the header or in the previous tabs), can also take the following values :
- mandatory value : only one of the values defined in the control table is authorized.
- prohibited value : all values are authorized, except the values listed in the control table.
- value range : the authorized values are defined within a range.
- table reference : the value must correspond to a principal key value in a table defined elsewhere.
- expression : a logic expression must be verified by a control value.