Different levels in the Lookup Table tree structures that have their own sub-levels.
An empty or blank value in a field. For example, a field has a null value if the user has not entered anything into the field. It is important to understand this term when writing rules because the Rules screen sometimes indicates that there is a null value selected in a qualifier by displaying (null). The
allowNullValue tag can also be used for custom fields of type Drop-down List.