When there is a select list field or a Keyword Type field configured with a Data Set, a self configured Data Set can be configured for a field. A self configured Data Set is a list of Data Set values that can be created and associated with a field on an ad hoc basis. Self configured Data Sets can be used by multiple fields in multiple forms.
To configure a self configured Data Set for a field:
You can specify that the value has to exist in the configured Data Set in order to submit the form by selecting the Value must exist property.