The optional temperatureUnit attribute defines the UnitName for the TemperatureValueType.
Source
<xs:element name="TargetValue" type="TemperatureValueType" minOccurs="0"><xs:annotation><xs:documentation>The optional TargetValue element is the nominal value of the temperature characteristic.</xs:documentation></xs:annotation></xs:element>
The id attribute is the QIF id of the characteristic, used for referencing.
Source
<xs:complexType name="TemperatureCharacteristicNominalBaseType" abstract="true"><xs:annotation><xs:documentation>The TemperatureCharacteristicNominalBaseType is the abstract base type that defines a unique temperature characteristic nominal.</xs:documentation></xs:annotation><xs:complexContent><xs:extension base="CharacteristicNominalBaseType"><xs:sequence><xs:element name="TargetValue" type="TemperatureValueType" minOccurs="0"><xs:annotation><xs:documentation>The optional TargetValue element is the nominal value of the temperature characteristic.</xs:documentation></xs:annotation></xs:element></xs:sequence></xs:extension></xs:complexContent></xs:complexType>