urdf error

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When I am trying to build my own robot according to this link: http://www.ros.org/wiki/urdf/Tutorials/Create%20your%20own%20urdf%20file

It appears to me some errors:

seec@ubuntu:~$ rosmake urdfdom_model [ rosmake ] rosmake starting...
[ rosmake ] Packages requested are: ['urdfdom_model']
[ rosmake ] Logging to directory /home/seec/.ros/rosmake/rosmake_output-20130722-140052 [ rosmake ] Expanded args ['urdfdom_model'] to: []
[ rosmake ] WARNING: The following args could not be parsed as stacks or packages: ['urdfdom_model'] [ rosmake ] ERROR: No arguments could be parsed into valid package or stack names. seec@ubuntu:~$ rosrun urdfdom_model check_urdf my_robot.urdf [rospack] Error: stack/package urdfdom_model not found

Is there some special place to save in it "my_robot.urdf" this .urdf file? I do not know what is the issue?