--- a/src/pyams_portal/interfaces/__init__.py	Thu Jun 21 16:38:12 2018 +0200
+++ b/src/pyams_portal/interfaces/__init__.py	Fri Jun 22 13:00:07 2018 +0200
@@ -25,7 +25,7 @@
 from pyams_security.schema import PermissionField
 from pyams_utils.schema import PersistentDict, PersistentList
 from zope.container.constraints import contains
-from zope.interface import invariant, Interface, Attribute, Invalid
+from zope.interface import Interface, Attribute
 from zope.schema import List, TextLine, Object, Int, Bool, Choice
 
 from pyams_portal import _
@@ -158,6 +158,8 @@
 
     target_interface = Attribute("Target interface provided by this renderer")
 
+    use_portlets_cache = Attribute("Can renderer use rendering cache?")
+
 
 PORTLET_RENDERER_SETTINGS_KEY = 'pyams_portal.renderer.settings::{0}'
 
@@ -391,6 +393,9 @@
     """
 
 
+PREVIEW_MODE = 'PREVIEW_MODE'
+
+
 class IPortalPage(Interface):
     """Portal page interface