-<!-- CONST is the constant string. -->
-<!-- The attributes binder and rvar declare variables which are -->
-<!-- referred to and used by means of respectively BINDER and RVAR -->
+<!-- CONST is the constant string; rvar is for references and lvar -->
+<!-- for list. -->
+<!-- The attributes binder, rvar, lvar declare variables which are -->
+<!-- referred to and used by means of respectively BINDER, Rvar and -->
+<!-- RVAR, Lvar and LVAR. -->
+<!-- Rvar (Lvar) is casted to a list, on the contrary the use of RVAR-->
+<!-- (LVAR) is casted to a string. -->
+<!-- PROPERTY works on a specified RDF property returning its value. -->