In your .htaccess file (maybe only in a specific folder) add this line to parse a .htm as a php file. This works on TxD accounts.

AddType application/x-httpd-php .htm .php

// description of your code here

#!/usr/bin/evn ruby
## to run this you call run_amazon_import(datafile) with dataflie = a file to open for parsing, which later is opened based on:
## ("#{RAILS_ROOT}/data/" + datafile + ".xml")
## This is hard coded to look at Item elements, and in this example
## parses out the ASIN as @@product_id and ItemAttributes/Title as @@name
## see check_position_space(name,ch)

require 'xml/saxdriver'
@flag_item  = false

  @@finaldata = []
  @@vars = []
  @@positionSpace = []
  @@currentName = []
def reset_vals
  @@product_id = nil
  @@name = nil
end
def check_position_space(name,ch)
  # with each value within item we check to see if the
  # @@positionSpace (a concatenation of each value's name
  # equals the value we are looking for, if so put it in a global 
  # variable
  if @@positionSpace == 'ASIN'
    @@product_id =  ch
  elsif @@positionSpace == 'ItemAttributesTitle'
        # if I did this again, I would name @@positionSpace
        # with / between names in startElement so it would be simlar to other 
        # ruby xml naming schems so:
        # @@positionSpace == 'ItemAttributesTitle' would be:
        # @@positionSpace == 'ItemAttributes/Title'
        @@name = ch
  end
end

class TestHandler < XML::SAX::HandlerBase
  attr_accessor :data
  def startDocument
    @@data = []
  end
  def startElement(name, attr)
    @flag_item = true if name == 'Item'
    @@positionSpace = '' if name == 'Item'
    if @flag_item == true and name != 'Item'
        @@positionSpace = @@positionSpace + name
    elsif name == 'Item'
      reset_vals
    end
    @@currentName = name
  end
  def endElement(name)
    if @flag_item == true and name != 'Item'
        lenName = name.length
        @@positionSpace = @@positionSpace[0, @@positionSpace.length - lenName]
    end
    if name == 'Item'
      @@finaldata  << @@data.to_s
      @@data = []
          ## Here I would have a fully parsed Item and do something with it
    end
    @flag_item = false if name == 'Item'
  end
  def characters(ch, start, length)
    check_position_space(@@currentName, ch[start, length])
  end
end

def run_amazon_import(datafile)
  @@datafile = datafile
  p = XML::SAX::Helpers::ParserFactory.makeParser("XML::Parser::SAXDriver")
  h = TestHandler.new
  p.setDocumentHandler(h)
  p.setDTDHandler(h)
  p.setEntityResolver(h)
  p.setErrorHandler(h)

  begin
    p.parse("#{RAILS_ROOT}/data/" + datafile + ".xml")
  rescue XML::SAX::SAXParseException
    p(["ParseError", $!.getSystemId, $!.getLineNumber, $!.getMessage])
  end
end

Доступ к дереву XML как к обычным объектам

Для этого можно использовать XSD::Mapping из стандартной библиотеки:

require ‘xsd/mapping’ 
people = XSD::Mapping.xml2obj(File.read("people.xml")) 
people.person[2].name # => "name3" 

Если в имени тэга присутствует дефис, можно сделать так: people[’foo-bar’]

Ну а выполнить обратное преобразование объектного дерева в XML поможет метод: XSD::Mapping.obj2xml