diff --git a/acs/attribute_aggregator/core.py b/acs/attribute_aggregator/core.py
index bf97edd..103b608 100644
--- a/acs/attribute_aggregator/core.py
+++ b/acs/attribute_aggregator/core.py
@@ -45,6 +45,21 @@ def iso8601_to_datetime(date_string):
     return datetime.datetime.fromtimestamp(time.mktime(tm))
 
 
+def get_all_attribute_definitions():
+    return ATTRIBUTE_MAPPING.keys()
+
+
+def get_all_sources():
+    from attribute_aggregator.models import AttributeSource
+    return AttributeSource.objects.all()
+
+
+def get_full_definition(definition):
+    if not definition in ATTRIBUTE_MAPPING:
+        return None
+    return ATTRIBUTE_MAPPING[definition]
+
+
 def get_def_name_from_name_and_ns_of_attribute(name, namespace):
     if not name or not namespace:
         return None
@@ -67,6 +82,13 @@ def get_attribute_name_in_namespace(definition, namespace):
     return None
 
 
+def get_attribute_type_of_definition(definition):
+    if not definition or not definition in ATTRIBUTE_MAPPING \
+            or not 'type' in ATTRIBUTE_MAPPING[definition]:
+        return None
+    return ATTRIBUTE_MAPPING[definition]["type"]
+
+
 def convert_from_string(definition_name, value):
     if not definition_name in ATTRIBUTE_MAPPING:
         return None
@@ -90,12 +112,12 @@ def convert_from_string(definition_name, value):
             return None
     elif type_ == ACS_XACML_DATATYPE_TIME:
         try:
-            return time.strptime(value,"%h:%m:%s") #12:15:00
+            return time.strptime(value, "%h:%m:%s") #12:15:00
         except:
             return None
     elif type_ == ACS_XACML_DATATYPE_DATE:
         try:
-            return time.strptime(value,"%d/%b/%Y") #28/01/1982
+            return time.strptime(value, "%d/%b/%Y") #28/01/1982
         except:
             return None
     elif type_ == ACS_XACML_DATATYPE_DATETIME:
@@ -180,12 +202,42 @@ def get_user_alias_in_source(user, source):
         return None
 
 
-def set_user_alias_in_source(user, source, name):
+def set_user_alias_in_source(user, source, name, force_change=False):
     from attribute_aggregator.models import UserAliasInSource
+    logger.debug('set_user_alias_in_source: set alias %s for user %s in \
+        source %s' % (name, user, source))
+    alias = None
     try:
-        alias, c = UserAliasInSource.objects.get_or_create(user=user,
-            source=source, name=name)
-        alias.save()
-        return alias
+        '''
+            If this user has already an alias, we change it.
+        '''
+        alias = UserAliasInSource.objects.get(user=user, source=source)
+        logger.warn('set_user_alias_in_source: \
+            this user has already an alias, we change it.')
+        alias.delete()
     except:
+        pass
+    try:
+        '''
+            If a user has already this alias...
+            force_change: we give it to this user
+        '''
+        alias = UserAliasInSource.objects.get(name=name, source=source)
+        if not force_change:
+            logger.warn('set_user_alias_in_source: \
+                a user has already this alias, we do nothing.')
+            return None
+        logger.warn('set_user_alias_in_source: \
+            a user has already this alias, we give it to %s.' % user)
+        alias.delete()
+    except:
+        pass
+    try:
+        alias = UserAliasInSource(user=user, name=name, source=source)
+        alias.save()
+        logger.debug('set_user_alias_in_source: alias created.')
+        return alias
+    except Exception, err:
+        logger.error('set_user_alias_in_source: unable to create alias due \
+            to %s.' % str(err))
         return None