Problem with urdf parsing

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URDF file

<xml version="1.0"?>
<robot name="rrbot">

<link name="base_link">
 <collision name="collision">
  <origin xyz="0 0 0.1" rpy="0 0 0"/>
  <geometry>
   <box size="0.4 0.2 0.1"/>
  </geometry>
 </collision>

<visual name="visual">
 <origin xyz="0 0 0.1" rpy="0 0 0"/>
 <geometry>
  <box size="0.4 0.2 0.1"/>
 </geometry>
</visual>

<inertial>
 <mass value="1e-5"/>
 <origin xyz="0 0 0.1" rpy="0 0 0"/>
 <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6"/>
</inertial>
</link>

<link name="left_wheel">
 <collision name="collision">
  <origin xyz="0.2 0.13 0.1" rpy="0 1.5707 1.5707"/>
  <geometry>
   <cylinder length="0.05" radius="0.1"/>
  </geometry>
 </collision>

<visual name="visual">
 <origin xyz="0.2 0.13 0.1" rpy="0 1.5705 1.5707"/>
 <geometry>
  <cylinder length="0.05" radius="0.1"/>
 </geometry>
</visual>
<inertial>
 <mass value="1e-5"/>
  <origin xyz="0.2 0.13 0.1"/>
  <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6"/>
 </inertial>
</link>

<joint type="revolute" name="joint1">

I was trying to execute this code but when I checked it using the command check_urdf rrbot.urdf I am getting an error mentioned below.

Error:   Error reading Attributes.
         at line 72 in /build/urdfdom-UJ3kd6/urdfdom-0.4.1/urdf_parser/src/model.cpp
ERROR: Model Parsing the xml failed

I need help.