Indicates the data element type from the value domain's point of view.
It can be one of the two following:
Element with fixed values (aka allowable values or code lists)
An element where predefined values are the only accepted values. In ISO 11179 terms referred as "characteristic 1"
or "characteristic of type 1".
Element with quantitative values (aka measured values)
An element that can have any values within the element's data type. In ISO 11179 terms referred as "characteristic 2"
or "characteristic of type 2". DD enables to define suggested values for these elements.
