variants 

The attribute variants defines the list of variants in which this Reference is valid. When the attribute is absent the Reference is valid in all variants.

Attribute Information

Used By

Attribute Group attlist.Reference

Source 

<xs:attribute name="variants" type="xs:IDREFS">
  <xs:annotation>
    <xs:documentation xml:lang="en-US">The attribute variants defines the list of variants in which this Reference is valid. When the attribute is absent the Reference is valid in all variants.</xs:documentation>
  </xs:annotation>
</xs:attribute>

Sample