Which attribute binding is effective?

So, what is the effective binding for an attribute? First? Last?

    

    Here is a scenario:

    

    Here is the contents of baseScheme.ditamap, which defines the os
    subject and binds its values to the @platform attribute:

    

    <subjectScheme>

          <subjectdef keys="os" navtitle="Operating system">

            <subjectdef keys="linux" navtitle="Linux">

              <subjectdef keys="redhat" navtitle="RedHat Linux"/>

              <subjectdef keys="suse"   navtitle="SuSE Linux"/>

            </subjectdef>

            <subjectdef keys="mswin" navtitle="Windows"/>

            <subjectdef keys="zos"   navtitle="z/OS"/>

          </subjectdef>

          <enumerationdef>

            <attributedef name="platform"/>

            <subjectdef keyref="os"/>

          </enumerationdef>

        </subjectScheme>

     

    Another subjectScheme map contains the following content:

    

    <subjectScheme>

          <schemeref href=""/>

          . . .

         <subjectdef keys="app" navtitle="Applications">

              <subjectdef keys="apacheserv" navtitle="Apache Web
        Server"/>

              <subjectdef keys="mysql"      navtitle="MySQL
        Database"/>

         </subjectdef>

      . . .

     
        <enumerationdef>

            <attributedef name="platform"/>

            <subjectdef keyref="app"/>

          </enumerationdef>

    </subjectScheme>

    

      
Best,

        Kris

        

        Kristen James Eberlein

        Principal consultant, Eberlein Consulting

        Co-chair, OASIS DITA Technical Committee

        Charter member, OASIS DITA Adoption Committee

        www.eberleinconsulting.com

        +1 919 682-2290; kriseberlein (skype)