mainEntry 

The attribute mainEntry allows defining if a index item is the main entry meaning that here is the best
description/use of this index item. Default is no.

Attribute Information

Used By

Attribute Group elml:IndexAttImp

Source 

<xs:attribute name="mainEntry" type="elml:YesNoType">
  <xs:annotation>
    <xs:documentation>The attribute mainEntry allows defining if a index item is the main entry meaning that here is the best description/use of this index item. Default is no.</xs:documentation>
  </xs:annotation>
</xs:attribute>

Sample