gistfile1.rb

require 'nokogiri'

doc = Nokogiri::XML(<<-eoxml)
<root>
 <car xmlns="http://gm.com/">
  <tire>Michelin Model XGV</tire>
 </car>
 <bicycle xmlns="http://schwinn.com/">
  <tire>I'm a bicycle tire!</tire>
 </bicycle>
</root>
eoxml

puts "bike tires"
# Only find bicycle tires
doc.xpath('//bike:tire', 'bike' => 'http://schwinn.com/').each do |node|
  p node
end

puts "car tires"
# Only find car tires
doc.xpath('//car:tire', 'car' => 'http://gm.com/').each do |node|
  p node
end