XHTML has several sets of common attributes (see XHTML 1.1).
For example, the core attributes:
<xs:attributeGroup name="Core"> <xs:attribute name="class" type="xs:NMTOKENS"/> <xs:attribute name="id" type="xs:ID"/> <xs:attribute name="title" type="xs:string"/> </xs:attributeGroup>
Some attribute groups are just aggregations:
<xs:attributeGroup name="Common"> <xs:attributeGroup ref="xhtml:Core"/> <xs:attributeGroup ref="xhtml:Events"/> <xs:attributeGroup ref="xhtml:I18N"/> <xs:attributeGroup ref="xhtml:Style"/> </xs:attributeGroup>