gistfile1.rb

Nokogiri::XML::Builder.new(:encoding => 'UTF-8') do |xml|
  osa = xml.add_namespace_declaration('osa', "http://www.onespot.com/Atom/Extensions/1.0")
  xml.feed :xmlns=>'http://www.w3.org/2005/Atom' do
    xml.div :xmlns=>'http://www.w3.org/1999/xhtml', :class=>'info' do
      xml.text "This is an Atom formatted XML site feed. It is intended to be viewed in a Newsreader or syndicated to another site."
    end

    xml.title   'feed title', :type=>"html"

    xml.entry do
      xml.title    'entry title', :type => "html"
      xml.score 0.50, :namespace => osa      ##### Want this to be an <osa:score> element
    end
  end
end.to_xml