FIXME 
<!ATTLIST variable remove_condition (True|False) "False">


<!ELEMENT condition ((target | param)+ )>
<!ATTLIST condition name (disabled_if_in|disabled_if_not_in|hidden_if_in|hidden_if_not_in|mandatory_if_in|mandatory_if_not_in) #REQUIRED>
<!ATTLIST condition source CDATA #REQUIRED>
<!ATTLIST condition fallback (True|False) "False">
<!ATTLIST condition force_condition_on_fallback (True|False) "False">
<!ATTLIST condition force_inverse_condition_on_fallback (True|False) "False">


on peut mettre plusieurs param (oui ou maybe)