diff --git a/plugins/pyloader/Makefile.am b/plugins/pyloader/Makefile.am
index 6cd6dda..b039648 100644
--- a/plugins/pyloader/Makefile.am
+++ b/plugins/pyloader/Makefile.am
@@ -146,6 +146,8 @@ MOSTLYCLEANFILES += $(proxies) $(wrappers)
 # built-in policies
 policies_PYTHON = \
        src/builtin-policies/fcfs.py \
+			 src/builtin-policies/lottery.py \
+			 src/builtin-policies/rr.py \
        src/builtin-policies/rr_priority.py \
        src/builtin-policies/sjf.py
 
diff --git a/plugins/pyloader/src/builtin-policies/fcfs.py b/plugins/pyloader/src/builtin-policies/fcfs.py
index 0e58f0b..04ed582 100644
--- a/plugins/pyloader/src/builtin-policies/fcfs.py
+++ b/plugins/pyloader/src/builtin-policies/fcfs.py
@@ -20,17 +20,19 @@
 
 
 from CPUPolicy import CPUPolicy
-import sys
-#from sgpem import policy_sorts_processes
 
 class fcfs(CPUPolicy) :
-    """First Come First Served"""
+    """First Come First Served scheduling policy.
+    
+The first thread to arrive to the CPU will run until
+it ends. This policy never pre-empts; it is probably
+the simplest of them all."""
     
     def __init__(self):
         pass;
 
     def configure(self):
-        print 'No options to configure for fcfs'
+        pass;
 
     def is_preemptive(self):
         return False
diff --git a/plugins/pyloader/src/builtin-policies/lottery.py b/plugins/pyloader/src/builtin-policies/lottery.py
new file mode 100644
index 0000000..b9ed3ef
--- /dev/null
+++ b/plugins/pyloader/src/builtin-policies/lottery.py
@@ -0,0 +1,48 @@
+# src/builtin-policies/lottery.py - Copyright 2005, 2006, University
+#                            of Padova, dept. of Pure and Applied
+#                            Mathematics
+#
+# This file is part of SGPEMv2.
+#
+# This is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# SGPEMv2 is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with SGPEMv2; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+
+
+from CPUPolicy import CPUPolicy
+from random import randint
+
+class lottery(CPUPolicy) :
+    """Lottery scheduling
+
+Every time slice, a thread will be selected from the ready
+queue by random. This policy does not pre-empt before the
+end of the time slice."""
+
+    def __init__(self):
+        pass;
+
+    def configure(self):
+        param = self.get_parameters()
+        param.register_int("Time slice", 1, 10000, True, 2)
+
+    def is_preemptive(self):
+        return False
+
+    def get_time_slice(self):
+        return self.get_parameters().get_int("Time slice")
+
+    def sort_queue(self, queue):
+        sz = queue.size()
+        if(sz > 0):
+            queue.swap(0, randint(0, sz - 1))
diff --git a/plugins/pyloader/src/builtin-policies/rr.py b/plugins/pyloader/src/builtin-policies/rr.py
new file mode 100644
index 0000000..a4523cc
--- /dev/null
+++ b/plugins/pyloader/src/builtin-policies/rr.py
@@ -0,0 +1,50 @@
+# src/builtin-policies/rr_priority.py - Copyright 2005, 2006, University
+#                            of Padova, dept. of Pure and Applied
+#                            Mathematics
+#
+# This file is part of SGPEMv2.
+#
+# This is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# SGPEMv2 is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with SGPEMv2; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+
+
+from CPUPolicy import CPUPolicy
+
+class rr(CPUPolicy) :
+    """Round Robin scheduling policy
+
+This policy executes a thread for a given amount
+of time (the time-slice value), and then puts it
+at the end of the queue. Does not pre-empt before
+the end of the time slice, since it doesn't take
+priority in account. Use rr_priority for that."""
+
+    def __init__(self):
+        pass;
+
+    def configure(self):
+        param = self.get_parameters()
+        param.register_int("Time slice", 1, 10000, True, 2)
+
+    def is_preemptive(self):
+        return False
+
+    def get_time_slice(self):
+        return self.get_parameters().get_int("Time slice")
+
+    def sort_queue(self, queue):
+        by_ltime = lambda a, b: \
+            a.get_last_acquisition() > \
+            b.get_last_acquisition()
+        self.sort(queue,by_ltime)
diff --git a/plugins/pyloader/src/builtin-policies/rr_priority.py b/plugins/pyloader/src/builtin-policies/rr_priority.py
index e1d11ac..ab1413b 100644
--- a/plugins/pyloader/src/builtin-policies/rr_priority.py
+++ b/plugins/pyloader/src/builtin-policies/rr_priority.py
@@ -20,9 +20,16 @@
 
 
 from CPUPolicy import CPUPolicy
-import sys
 
 class rr_priority(CPUPolicy) :
+    """Round Robin scheduling policy that takes priority in account. 
+    
+No lower priority thread can run if a higher 
+priority thread exists. If pre-emptive by priority, a 
+higher-priority thread becoming ready even in the middle
+of a time slice will pre-empt the running thread. Else,
+the time slice will have to end before the former can run."""
+
     def __init__(self):
         pass;
 
@@ -38,7 +45,6 @@ class rr_priority(CPUPolicy) :
         else:
             return True
 
-    # FIXME pass to a configurable amount
     def get_time_slice(self):
         return self.get_parameters().get_int("Time slice")
 
diff --git a/plugins/pyloader/src/builtin-policies/sjf.py b/plugins/pyloader/src/builtin-policies/sjf.py
index d26991b..b9e8a68 100644
--- a/plugins/pyloader/src/builtin-policies/sjf.py
+++ b/plugins/pyloader/src/builtin-policies/sjf.py
@@ -20,18 +20,30 @@
 
 
 from CPUPolicy import CPUPolicy
-import sys
-#from sgpem import policy_sorts_processes
 
 class sjf(CPUPolicy) :
+    """Shortest Job First scheduling policy
+
+The thread with the shortest required CPU time
+will run until it ends. If pre-emptive is set
+to true, if a shorter thread arrives at the CPU
+at a given moment, it will pre-empt the running
+one. The policy is also called Shortest Remaining
+Time Next in this case."""
+
     def __init__(self):
         pass;
 
     def configure(self):
-        print 'No options to configure for fcfs'
+        params = self.get_parameters()
+        params.register_int("Is preemptive?", 0, 1, True, 0)
 
     def is_preemptive(self):
-        return False
+        value = self.get_parameters().get_int("Is preemptive?")
+        if value == 0:
+            return False
+        else:
+            return True
 
     def get_time_slice(self):
         return -1
diff --git a/plugins/pyloader/src/python_cpu_policy.cc b/plugins/pyloader/src/python_cpu_policy.cc
index 2608920..40e9d5f 100644
--- a/plugins/pyloader/src/python_cpu_policy.cc
+++ b/plugins/pyloader/src/python_cpu_policy.cc
@@ -61,7 +61,9 @@ PythonCPUPolicy::PythonCPUPolicy(const char* name) throw(MalformedPolicyExceptio
 
   // Now takes the user-defined policy class from pUserCPUPolicyDict
   PyObject* pCPUPolicyClass = PyDict_GetItemString(_upolicy_dict, name);
-  assert(pCPUPolicyClass); // FIXME needs stricter checking and exception throwing
+  if (pCPUPolicyClass == NULL)
+    throw MalformedPolicyException(Glib::ustring(_("Cannot find a class named ")) + 
+                                   name + _(" into the corresponding .py file."));
 
   // Retrieve a description for the policy using the __doc__ attribute
   PyObject* pDescriptionString = PyObject_GetAttrString(pCPUPolicyClass, "__doc__");
diff --git a/src/gui_builder.cc b/src/gui_builder.cc
index 0961b27..f0ed047 100644
--- a/src/gui_builder.cc
+++ b/src/gui_builder.cc
@@ -610,8 +610,8 @@ SimulationController::run_simulation_adaptor()
     catch(const MalformedPolicyException& mpe)
       {
         // Show user a dialog
-        MessageDialog diag(_("<b>The selected user CPU policy was malformed and didn't run:</b>\n") + Markup::escape_text(mpe.what()), 
-                           true, Gtk::MESSAGE_ERROR, Gtk::BUTTONS_OK, true);
+        MessageDialog diag(_("<b>The selected user CPU policy was malformed and failed to sort the queue:</b>\n") + 
+                           Markup::escape_text(mpe.what()), true, Gtk::MESSAGE_ERROR, Gtk::BUTTONS_OK, true);
         diag.run();
    
         try