The example in 15.8 Examples of xsl:merge still make use of bind-key attribute

[[
<xsl:merge bind-key="merge-key">
  <xsl:merge-source name="master" 
                    select="doc('master.xml')/data/record">
      <xsl:merge-key select="@ID"/>
  </xsl:merge-source>
  <xsl:merge-source name="updates"
                    sort-before-merge="yes"
                    select="doc('transactions.xml')/transactions/update">     
      <xsl:merge-key select="@record"/>
  </xsl:merge-source>
  <xsl:merge-action>
    <xsl:choose>
      <xsl:when test="empty(current-merge-group('updates'))">
        <xsl:copy-of select="current-merge-group('master')"/>
      </xsl:when>
      <xsl:when test="current-merge-group('updates')/@action=('insert', 'replace')">
        <record ID="{$merge-key}">
          <xsl:copy-of select="current-merge-group('updates')/*"/>
        </record>
      </xsl:when>
      <xsl:when test="current-merge-group('updates')/@action='delete'"/>
    </xsl:choose>
  </xsl:merge-action>
  </xsl:merge>
]]