NVDL, DocBook, and MathML

The DocBook rng schema for inlineequation is as follows:

   <define name="db.inlineequation.content">
      <choice>
         <choice>
            <oneOrMore>
               <ref name="db.inlinemediaobject"/>
            </oneOrMore>
            <oneOrMore>
               <ref name="db.mathphrase"/>
            </oneOrMore>
         </choice>
         <oneOrMore>
            <ref name="db._any.mml"/>
         </oneOrMore>
      </choice>
   </define>