diff --git a/GPL/aggregate.pl b/GPL/aggregate.pl
index a6493b806..5bdcb9bae 100644
--- a/GPL/aggregate.pl
+++ b/GPL/aggregate.pl
@@ -1,4 +1,4 @@
-/*  $Id: aggregate.pl,v 1.1 2008-02-12 17:03:52 vsc Exp $
+/*  $Id: aggregate.pl,v 1.2 2008-02-12 18:10:48 vsc Exp $
 
     Part of SWI-Prolog
 
@@ -42,6 +42,10 @@
 :- use_module(library(error)).
 :- use_module(library(lists)).
 
+:- if(current_prolog_flag(dialect, yap)).
+:- use_module(library(maplist)).
+:- endif.
+
 :- module_transparent
 	foreach/2,
 	aggregate/3,
diff --git a/LGPL/prolog_xref.pl b/LGPL/prolog_xref.pl
index b7f079d2e..10bc11ad7 100644
--- a/LGPL/prolog_xref.pl
+++ b/LGPL/prolog_xref.pl
@@ -1,4 +1,4 @@
-/*  $Id: prolog_xref.pl,v 1.1 2008-02-12 17:03:54 vsc Exp $
+/*  $Id: prolog_xref.pl,v 1.2 2008-02-12 18:10:48 vsc Exp $
 
     Part of SWI-Prolog
 
@@ -118,6 +118,8 @@ genarg(X,Y,Z) :-
 :- else.
 % yap
 
+:- ensure_loaded(library(swi)).
+
 :- user_defined_flag(xref).
 
 :- use_module(library(arg)).
diff --git a/library/swi.yap b/library/swi.yap
index cfee4fb53..b6803ac60 100644
--- a/library/swi.yap
+++ b/library/swi.yap
@@ -23,10 +23,10 @@
 			      term_hash/2,
 			      variant/2]).
 
-:- multifile
+:- dynamic
    prolog:message/3.
 
-:- dynamic
+:- multifile
    prolog:message/3.
 
 :- multifile
@@ -174,9 +174,17 @@ prolog:nth1(I,L,A) :- nth(I,L,A).
 
 prolog:prolog_to_os_filename(X,X).
 
+prolog:is_absolute_file_name(X) :-
+	absolute_file_name(X,X).
+
+prolog:read_clause(X,Y) :-
+	read_term(X,Y,[singetons(warning)]).
+
 prolog:forall(X,Y) :- 
 	catch(do_forall(X,Y), fail_forall, fail).
 
+prolog:string(_) :- fail.
+
 do_forall(X,Y) :-
 	call(X),
 	do_for_forall(Y).