The FeatureNominalIds element is a list of QIF ids of the set of feature items comprising the group feature. Having a single QIF id in the list is OK because it is allowable to reference another group feature.
The required n attribute is the number of Id elements in this array.
Source
<xs:element name="FeatureNominalIds" type="ArrayReferenceFullType"><xs:annotation><xs:documentation>The FeatureNominalIds element is a list of QIF ids of the set of feature items comprising the group feature. Having a single QIF id in the list is OK because it is allowable to reference another group feature.</xs:documentation></xs:annotation></xs:element>
The id attribute is the QIF id of the feature, used for referencing.
Source
<xs:complexType name="GroupFeatureNominalType"><xs:annotation><xs:documentation>The GroupFeatureNominalType is defines the group feature nominal information for an individual group feature.</xs:documentation></xs:annotation><xs:complexContent><xs:extension base="ShapeFeatureNominalBaseType"><xs:sequence><xs:element name="FeatureNominalIds" type="ArrayReferenceFullType"><xs:annotation><xs:documentation>The FeatureNominalIds element is a list of QIF ids of the set of feature items comprising the group feature. Having a single QIF id in the list is OK because it is allowable to reference another group feature.</xs:documentation></xs:annotation></xs:element></xs:sequence></xs:extension></xs:complexContent></xs:complexType>