1<!ELEMENT tree (branch+)>
2<!ELEMENT branch (branchText,(branch|leaf|branchLink)*)>
3<!ATTLIST branch id CDATA #REQUIRED>
4<!ATTLIST branch link CDATA #REQUIRED>
5<!ELEMENT leaf (leafText,link)>
6<!ELEMENT branchLink (branchText,link)>
7<!ATTLIST branchLink id CDATA #REQUIRED>
8<!ELEMENT leafText (#PCDATA)>
9<!ELEMENT link (#PCDATA)>
10