anchor.diff:        e2=EXISTS 
         { ec = new ExistsCondition($e2); 
           $condition = ec; }
  -      specifiedConditionVariable 
  -      { ec.setVariable($specifiedConditionVariable.variable); }
  +      specifiedVariable 
  +      { ec.setVariable($specifiedVariable.variable); }
       //-> ^(EXISTS_CONDITION[$EXISTS] specifiedVariable2)
       | //(EXISTS LIDENTIFIER (RPAREN|COMMA)) =>
         e1=EXISTS
  
positive.code:         de2=disjunctionExpression
          { $thenElseOperator.operator.setRightTerm($de2.term); }
        )*
      | 
        ( existsCondition | nonemptyCondition | isCondition | 
          TYPE_CONSTRAINT specifiedConditionVariable )+
        THEN_CLAUSE disjunctionExpression 
        (ELSE_CLAUSE disjunctionExpression)?
      ;
  
  thenElseOperator returns [BinaryOperatorExpression operator]
  
negative.code:       { $specifierExpression.setExpression($functionOrExpression.expression); }
      ;
  
  lazySpecifier returns [SpecifierExpression specifierExpression]
      : COMPUTE
        { $specifierExpression = new LazySpecifierExpression($COMPUTE); }
  