The PatternFeatureDefinitionBaseType is the abstract base type that defines the pattern feature nominal information that can be common to one or more pattern features.
The id attribute is the QIF id of the feature, used for referencing.
Source
<xs:complexType name="PatternFeatureDefinitionBaseType" abstract="true"><xs:annotation><xs:documentation>The PatternFeatureDefinitionBaseType is the abstract base type that defines the pattern feature nominal information that can be common to one or more pattern features.</xs:documentation></xs:annotation><xs:complexContent><xs:extension base="GroupFeatureDefinitionType"/></xs:complexContent></xs:complexType>