The id attribute is the QIF id of the model entity, used for referencing.
Source
<xs:element name="Entity" type="EntityExternalType" maxOccurs="unbounded"><xs:annotation><xs:documentation>Each Entity element gives the association of a QIF id with a model entity.</xs:documentation></xs:annotation></xs:element>
The required n attribute is the number of external model entities in the list.
Source
<xs:complexType name="EntitiesExternalType"><xs:annotation><xs:documentation>The EntitiesExternalType defines a list of external model entities.</xs:documentation></xs:annotation><xs:sequence><xs:element name="Entity" type="EntityExternalType" maxOccurs="unbounded"><xs:annotation><xs:documentation>Each Entity element gives the association of a QIF id with a model entity.</xs:documentation></xs:annotation></xs:element></xs:sequence><xs:attribute name="n" type="NaturalType" use="required"><xs:annotation><xs:documentation>The required n attribute is the number of external model entities in the list.</xs:documentation></xs:annotation></xs:attribute></xs:complexType>
<xs:attribute name="n" type="NaturalType" use="required"><xs:annotation><xs:documentation>The required n attribute is the number of external model entities in the list.</xs:documentation></xs:annotation></xs:attribute>