*****************************************************************************)
+let init () = () (* FG: implementare l'apertura del database *)
+
+let close () = () (* FG: implementare la chiusura del database *)
+
+
+(* contexts *****************************************************************)
+
type svar_context = (MathQL.svar * MathQL.resource_set) list
type rvar_context = (MathQL.rvar * MathQL.resource) list