anchor.diff:  orExpr
       : andExpr ( "or"^ andExpr )*
       ;
  -    
  +
   andExpr
       : atom ( "and"^ atom )*
       ;
  
positive.code: IDENTIFIER
      :  ('a'..'z'|'_') ('a'..'z'|'_'|'0'..'9')*
      ;
      
  
negative.code: //
  // Grammar for path expressions
  //
  
  header {
  