From 1c462f5916be3f41bd48b1146d0c39e3f5c643a3 Mon Sep 17 00:00:00 2001
From: Christophe Bedard <bedard.christophe@gmail.com>
Date: Mon, 27 May 2019 14:45:46 +0200
Subject: [PATCH] Add first version of 'message publishing' section

---
 doc/ros_2.md | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/doc/ros_2.md b/doc/ros_2.md
index f4c5cfc..fc287aa 100644
--- a/doc/ros_2.md
+++ b/doc/ros_2.md
@@ -187,3 +187,24 @@ sequenceDiagram
     end
     Executor->>Subscription: return_message(msg)
 ```
+
+### Message publishing
+
+To publish a message, an object is first allocated and then populated by the `Component` (or equivalent). Then, the message is sent to the `Publisher` through `publish()`. This then passes that on to `rcl`, which itself passes it to `rmw`.
+
+TODO add inter- vs. intra-process execution flow
+TODO talk about IntraProcessManager stuff?
+
+```mermaid
+sequenceDiagram
+    participant Component
+    participant Publisher
+    participant rcl
+    participant tracetools
+
+    Note over Component: creates a msg
+    Component->>Publisher: publish(msg)
+    Note over Publisher: ...
+    Publisher->>rcl: rcl_publish(rcl_publisher_t, msg)
+    rcl->>rmw: rmw_publisher(rmw_publisher, msg)
+```