anchor.diff:  
   //root level boolean expression
   expression:
  - orexp;
  -// | '('expression')';
  -
  -
  +  orexp;
  +
  +//direction for ordering
   direction  : ('asc' | 'desc');
   
  +//order cause
   order
     : (property direction?);
   
  
positive.code: 
  q = query;
  
  };
  
  //
  
negative.code:   
  //
  operation :
   '('! expression ')'! | equalityop | locationop | containsop;
  
  //negations of operations
  notexp :
  