<configure xmlns="http://namespaces.zope.org/zope"
           xmlns:zcml="http://namespaces.zope.org/zcml">
  
  <include package="plone.dexterity" file="meta.zcml" />
  <include zcml:condition="installed plone.directives.dexterity"
           package="plone.directives.dexterity" file="meta.zcml" />
  <include zcml:condition="installed plone.directives.form"
           package="plone.directives.form" file="meta.zcml" />
  
</configure>