require 'nokogiri'
require "rexml/document"
test = "system.webServer"

builder = Nokogiri::XML::Builder.new do
	location do
		system2222 do
			advancedLogging do
				server do
					logDefinitions do
						logDefinition do
							selectedFields do
								logField(:id => "Date-UTC", :logHeaderName => "date", :required => "false")
							end
						end
					end
				end
			end
		end
	end
end

doc = Nokogiri::XML(IO.read("d:/games/games/test.xml"))
doc.root.add_child builder.doc.root

file = File.open("d:/games/games/test.xml",'w')
source =  doc.to_xml
doc = REXML::Document.new(source)
formatter = REXML::Formatters::Pretty.new
formatter.compact = true
formatter.write(doc, file)
file.close