<!ELEMENT change ( table-name, schema-from, schema-to, (add, alter, remove)+ ) >

<!ELEMENT schema-from ( schema-major, schema-minor ) >
<!ELEMENT schema-to ( schema-major, schema-minor ) >
<!ELEMENT add ( (column, key, index)+ ) >
<!ELEMENT alter ( column+ ) >
<!ELEMENT remove ( (column-name, key, index)+ ) >
<!ELEMENT column ( column-name, column-type, column-size, not-null? ) >
<!ELEMENT key ( column-name+ ) >
<!ELEMENT index ( column-name+ ) >

<!ELEMENT table-name ( #PCDATA ) >
<!ELEMENT schema-major ( #PCDATA ) >
<!ELEMENT schema-minor ( #PCDATA ) >
<!ELEMENT column-name ( #PCDATA ) >
<!ELEMENT column-type ( #PCDATA ) >
<!ELEMENT column-size ( SMALL | MEDIUM | LARGE ) >
<!ELEMENT not-null EMPTY >
<!ELEMENT null EMPTY >
<!ATTLIST not-null empty (allowed | disallowed) "disallowed">