If this element is set to true, the declared fied/component/sub-component shall be present If this element is set to false, the declared field/component/sub-component shall not be present A specific set of values in which the value of the specified field/component/sub-component must be Defines a value set available in our SVS repository A list of strings in which the value must be reference to the HL7 table to use reference to the user defined table to use