P5: Guidelines for Electronic Text Encoding and Interchange

<rng:element name="charDecl">
 <rng:ref name="att.global.attributes"/>
 <rng:group>
  <rng:optional>
   <rng:ref name="desc"/>
  </rng:optional>
  <rng:oneOrMore>
   <rng:choice>
    <rng:ref name="char"/>
    <rng:ref name="glyph"/>
   </rng:choice>
  </rng:oneOrMore>
 </rng:group>
</rng:element>

element charDecl { att.global.attributes, ( desc?, ( char | glyph )+ ) }