diff --git a/tracetools_analysis/analysis/data_model.py b/tracetools_analysis/analysis/data_model.py
index 48179c9..f6bbe77 100644
--- a/tracetools_analysis/analysis/data_model.py
+++ b/tracetools_analysis/analysis/data_model.py
@@ -47,10 +47,10 @@ class DataModel():
     def add_subscription(self, subscription_handle, timestamp, node_handle, rmw_handle, topic_name, depth):
         self._subscriptions.loc[subscription_handle] = [timestamp, node_handle, rmw_handle, topic_name, depth]
 
-    def add_subscription_callback_object(self, subscription_handle, timestamp, callback_object):
-        self._callback_objects.loc[subscription_handle] = [timestamp, callback_object]
+    def add_callback_object(self, handle, timestamp, callback_object):
+        self._callback_objects.loc[handle] = [timestamp, callback_object]
 
-    def add_callback(self, callback_object, timestamp, symbol):
+    def add_callback_symbol(self, callback_object, timestamp, symbol):
         self._callback_symbols.loc[callback_object] = [timestamp, symbol]
     
     def add_callback_instance(self, callback_object, timestamp, duration, intra_process):
@@ -67,8 +67,6 @@ class DataModel():
         print()
         print(f'Subscriptions:\n{self._subscriptions.to_string()}')
         print()
-        print(f'Callback instances:\n{self._callbacks_instances.to_string()}')
-        print()
         print(f'Services:\n{self._services.to_string()}')
         print()
         print(f'Clients:\n{self._clients.to_string()}')
@@ -78,4 +76,6 @@ class DataModel():
         print(f'Callback objects:\n{self._callback_objects.to_string()}')
         print()
         print(f'Callback symbols:\n{self._callback_symbols.to_string()}')
+        print()
+        print(f'Callback instances:\n{self._callbacks_instances.to_string()}')
         print('==================================================')
diff --git a/tracetools_analysis/analysis/processor.py b/tracetools_analysis/analysis/processor.py
index d8c0b46..0afb2de 100644
--- a/tracetools_analysis/analysis/processor.py
+++ b/tracetools_analysis/analysis/processor.py
@@ -102,27 +102,13 @@ class RosProcessor(EventHandler):
     def _handle_rclcpp_subscription_callback_added(self, event, metadata):
         subscription_handle = get_field(event, 'subscription_handle')
         callback_object = get_field(event, 'callback')
-        self._data.add_subscription_callback_object(subscription_handle, metadata.timestamp, callback_object)
+        self._data.add_callback_object(subscription_handle, metadata.timestamp, callback_object)
 
     def _handle_rclcpp_subscription_callback_start(self, event, metadata):
-        # Add to dict
-        callback_addr = get_field(event, 'callback')
-        self._callback_instances[callback_addr] = (event, metadata)
+        self.__handle_callback_start(event, metadata)
 
     def _handle_rclcpp_subscription_callback_end(self, event, metadata):
-        # Fetch from dict
-        callback_object = get_field(event, 'callback')
-        (event_start, metadata_start) = self._callback_instances.get(callback_object)
-        if event_start is not None and metadata_start is not None:
-            del self._callback_instances[callback_object]
-            duration = metadata.timestamp - metadata_start.timestamp
-            is_intra_process = get_field(event_start, 'is_intra_process')
-            self._data.add_subscription_callback_instance(callback_object,
-                                                          metadata_start.timestamp,
-                                                          duration,
-                                                          bool(is_intra_process))
-        else:
-            print(f'No matching callback start for callback object "{callback_object}"')
+        self.__handle_callback_end(event, metadata)
 
     def _handle_rcl_service_init(self, event, metadata):
         # TODO
@@ -163,4 +149,24 @@ class RosProcessor(EventHandler):
     def _handle_rclcpp_callback_register(self, event, metadata):
         callback_object = get_field(event, 'callback')
         symbol = get_field(event, 'symbol')
-        self._data.add_callback(callback_object, metadata.timestamp, symbol)
+        self._data.add_callback_symbol(callback_object, metadata.timestamp, symbol)
+
+    def __handle_callback_start(self, event, metadata):
+        # Add to dict
+        callback_addr = get_field(event, 'callback')
+        self._callback_instances[callback_addr] = (event, metadata)
+
+    def __handle_callback_end(self, event, metadata):
+        # Fetch from dict
+        callback_object = get_field(event, 'callback')
+        (event_start, metadata_start) = self._callback_instances.get(callback_object)
+        if event_start is not None and metadata_start is not None:
+            del self._callback_instances[callback_object]
+            duration = metadata.timestamp - metadata_start.timestamp
+            is_intra_process = get_field(event_start, 'is_intra_process', raise_if_not_found=False)
+            self._data.add_callback_instance(callback_object,
+                                             metadata_start.timestamp,
+                                             duration,
+                                             bool(is_intra_process))
+        else:
+            print(f'No matching callback start for callback object "{callback_object}"')