$ awk -F'["<>]+' '/^<Key DeviceID=/{cmd="x "$3" "$5".dat";print cmd;system(cmd)}' UR.xml
x aaa 111.dat
sh: 1: x: not found <==you need check "x aaa 111.dat" command by yourself that can run well in your system.
x bbb 222.dat
sh: 1: x: not found
x ccc 333.dat
sh: 1: x: not found