<!ELEMENT Document (Title, Description, Summary?, (Chapter | ExternalChapter)*, Appendix*)>
<!ATTLIST Document version CDATA #FIXED "1.0">
<!ELEMENT Summary (Title, ExternalDiagram?, Body)>
-<!ELEMENT Appendix (Title, ExternalDiagram?, Body, Section*)>
-<!ELEMENT Chapter (Title, ExternalDiagram?, Body, Section*)>
-<!ELEMENT Section (Title, ExternalDiagram?, Body, SubSection*)>
+<!ELEMENT Appendix (Title, ExternalDiagram?, Body?, Section*)>
+<!ELEMENT Chapter (Title, ExternalDiagram?, Body?, Section*)>
+<!ELEMENT Section (Title, ExternalDiagram?, Body?, SubSection*)>
<!ELEMENT SubSection (Title, ExternalDiagram?, Body)>
<!ELEMENT Title (#PCDATA)>
+<!ELEMENT Description (#PCDATA)>
<!ELEMENT Body (ExternalDiagram | p)*>
<!ELEMENT p ANY>
<!ELEMENT ExternalDiagram (#PCDATA)>