diff --git a/doc/ros_2.md b/doc/ros_2.md
index 923f293..b912124 100644
--- a/doc/ros_2.md
+++ b/doc/ros_2.md
@@ -219,3 +219,11 @@ sequenceDiagram
     Publisher->>rcl: rcl_publish(rcl_publisher_t, msg)
     rcl->>rmw: rmw_publisher(rmw_publisher, msg)
 ```
+
+### Service creation
+
+### Timer creation
+
+### Service callbacks
+
+### Timer callbacks