anchor.diff:  
   typeFieldSpec : AMPERSAND IDENTIFIER typeOptionalitySpec?
   ;
  -typeOptionalitySpec : OPTIONAL_LITERAL | (DEFAULT_LITERAL type)
  -;
  -fixedTypeValueFieldSpec : AMPERSAND IDENTIFIER type UNIQUE_LITERAL? valueOptionalitySpec ?
  +typeOptionalitySpec : OPTIONAL_LITERAL | (DEFAULT_LITERAL asnType)
  +;
  +fixedTypeValueFieldSpec : AMPERSAND IDENTIFIER asnType UNIQUE_LITERAL? valueOptionalitySpec ?
   ;
   valueOptionalitySpec : OPTIONAL_LITERAL | (DEFAULT_LITERAL value)
   ;
  
positive.code: variableTypeValueFieldSpec : AMPERSAND IDENTIFIER  fieldName valueOptionalitySpec ?
  ;
  
  fixedTypeValueSetFieldSpec : AMPERSAND IDENTIFIER   type valueSetOptionalitySpec ?
  ;
  
  valueSetOptionalitySpec : OPTIONAL_LITERAL | DEFAULT_LITERAL valueSet
  
negative.code: //dummyGovernor : dummyReference
  //;
  
  governor : asnType | definedObjectClass
  ;
  
  
  