Merge pull request #18 from microROS/post/system_modes_initial

Post/system modes initial

Author: Iñigo Muguruza

_data/authors.yml

@@ -1,2 +1,6 @@
 iluetkeb:
   twitter: ingoluetkebohle
+anordman:
+  name: Arne Nordmann
+  twitter: norro58
+  web: http://arne-nordmann.de

_posts/2019-03-19-system-modes-released.md

@@ -0,0 +1,8 @@
+---
+title:  "ROS 2 System Modes package released"
+author: anordman
+---
+
+We just released the **[ROS 2 system modes package](https://github.com/microROS/system_modes)** that implements our attempt to allow behavioral system composition for ROS 2. *System modes* assume that the system is built from components with a lifecycle (see [ROS 2 managed nodes](https://index.ros.org/doc/ros2/Tutorials/Managed-Nodes/)). It adds a **notion of (sub-)systems**, hierarchically grouping these nodes, as well as a **notion of modes** that determine the configuration of these nodes and (sub-)systems in terms of their parameter values. 
+
+Check the [system_modes example package](https://github.com/microROS/system_modes/tree/master/system_modes_examples) for a small step-by-step example. For more information, check the [ROS wiki](http://wiki.ros.org/system_modes) and the [system_modes package on github](https://github.com/microROS/system_modes).