<!ELEMENT extensions (value-object|sql-query-method|custom-method)*>
<!ELEMENT value-object (add-column+)>
<!ATTLIST value-object 
   name CDATA #REQUIRED
   base-table CDATA #REQUIRED>
<!ELEMENT add-column EMPTY>
<!ATTLIST add-column 
   table CDATA #REQUIRED
   column-name CDATA #REQUIRED>
<!ELEMENT sql-query-method (parameter*,where)>
<!ATTLIST sql-query-method 
   name CDATA #REQUIRED
   value-object CDATA #REQUIRED>
<!ELEMENT parameter EMPTY>
<!ATTLIST parameter 
   name CDATA #REQUIRED>
<!ELEMENT where (#PCDATA)>
<!ELEMENT custom-method (parameter*)>
<!ATTLIST custom-method 
   name CDATA #REQUIRED
   table CDATA #REQUIRED
   return-type CDATA #REQUIRED>