Explaining the xacro model of the seven DOF arm

We will define ten links and nine joints on this robot, and two links and two joints in the robot gripper.

Let's start by looking at the xacro definition:

<?xml version="1.0"?> 
<robot name="seven_dof_arm" xmlns:xacro="http://ros.org/wiki/xacro">  

Because we are writing a xacro file, we should mention the xacro namespace to parse the file.