Merkede seksjoner

Merkede seksjoner forutsetter et 'internt subsett':

    <!DOCTYPE book PUBLIC"-//OASIS//DTD DocBook V4.1//EN"[
      <!ENTITY % db-oracle "IGNORE">
      <!ENTITY % db-ibmdb2 "IGNORE">
      <!ENTITY % appserv-websphere "IGNORE">
      <!ENTITY % appserv-silverstream "IGNORE">
      <!ENTITY % os-mswin "IGNORE">
      <!ENTITY % os-solaris "IGNORE">
      <!ENTITY % print "IGNORE">
      <!ENTITY % online "IGNORE">
      <!ENTITY conceptsoverview.sgm SYSTEM "concepts_with_cond.sgm">
      ]>
      . . .
      <book>
      <title>
      Installing on <![%os-mswin;[Microsoft Windows NT/2000]]><![%os-solaris;[Solaris]]> servers 
      running <![%db-oracle;[Oracle]]><![%db-ibmdb2;[IBM DB2]]> database and <
      ![%appserv-silverstream;[SilverStream]]><![%appserv-websphere;[IBM WebSphere]]> application server
      </title>
      <chapter> . . .  </chapter>
      </book>