From http://www.openwddx.org/faq/:
WDDX is an XML-based technology that enables the exchange of complex data between Web programming languages,
creating what some refer to as 'Web syndicate networks'.
WDDX consists of a language-independent representation of data based on an XML 1.0 DTD, and a set of
modules for a wide variety of languages that use WDDX.
WDDX can be used with HTTP, SMTP, POP, FTP and other Internet protocols that support transferring textual data.

WDDX Home: http://www.openwddx.org/

The Ruby WDDX Gem enables easy usage of WDDX in Ruby.

== Author

Copyright (C) 2005, 2006, 2007 by Stefan Saasen <s-NOSPAM-REMOVE@juretta.com> - http://juretta.com/

== Installation

Just run <tt>[sudo] gem install wddx</tt> to install the WDDX Gem.

== Deserialization
You can very easily deserialize WDDX data from a file or from a string.

Simple usage example:

require 'rubygems'
require 'wddx'
# data.xml contains <?xml version="1.0">\
# <wddxPacket version='1.0'><header><comment>A comment</comment></header><data><string>Klaus Tester</string></data></wddxPacket>
wddx = WDDX.load(File.open("data.xml"))
puts wddx.comment # "A comment"
puts wddx.data.class # String
puts wddx.data # "Klaus Tester"

WDDX.load accepts a string with xml content, a file object or any object that provides a +read+ method.
packet = WDDX.load(open("http://wddx.rubyforge.org/wddx.xml"))
packet = WDDX.load(File.open("data.xml"))
packet = WDDX.load(open("data.xml"))
xml = "<wddxPacket version='1.0'><header/><data><number>123.667</number></data></wddxPacket>"
packet = WDDX.load(xml)
puts w.data # => 123.667

xml = <<-EOF
<wddxPacket version='1.0'>
<var name='aNull'>
<var name='aString'>
<string>a string</string>
w = WDDX.load(xml)
p w.data # => string", "aNull"=>nil

If the root element is a +struct+ you can use a shortcut version:

w.data["aString"] # => "a string"

can be written as:

w.aString # => "a string"

== Serialization
The core Ruby Classes +Symbol+, +String+, +Numeric+, +true+, +false+, +nil+, +Hash+, +Array+ and +Time+ can be serialized by calling

require 'wddx'
"Stefan Saasen".to_wddx # => "<wddxPacket version='1.0'><header/><data>\
# <string>Stefan Saasen</string></data></wddxPacket>"

123.667.to_wddx # => "<wddxPacket version='1.0'><header/><data>\
# <number>123.667</number></data></wddxPacket>"

Math::PI.to_wddx # => "<wddxPacket version='1.0'><header/><data>\
# <number>3.14159265358979</number></data></wddxPacket>"

[1000, "Klaus Tester"].to_wddx # => "<wddxPacket version='1.0'><header/><data>\
# <array length='2'><number>1000</number>\
# <string>Klaus Tester</string></array></data></wddxPacket>"

=== WDDX.dump
You can use WDDX.dump to serialize Ruby objects.
WDDX.dump("Hallo Welt") # => "<wddxPacket version='1.0'><header/><data><string>Hallo Welt</string></data></wddxPacket>"

Custom Ruby classes can be serialized by adding a +to_wddx_properties+ method (in the style of the YAML library) and calling WDDX.dump.

class SerializeFromOutside
def initialize(a,b,c)
@a, @b, @c = a, b, c

def to_wddx_properties
["@a", "@c"]
obj = SerializeFromOutside.new("This is a", "This is b", 123)
WDDX.dump(obj) # => "<wddxPacket version='1.0'><header/><data><struct><var name='a'>\
# <string>This is a</string></var><var name='c'><number>123</number>\
# </var></struct></data></wddxPacket>"

It is possible to include the WDDX module to get a behaviour similiar to the core Ruby classes.

class MyObject
include WDDX
attr_accessor :name, :value, :price

def to_wddx_properties
["@name", :custom_price]

def custom_price
@price * 1.05

obj = MyObject.new("Stefan Saasen", 120)
puts ob.to_wddx
# => "<wddxPacket version='1.0'><header/><data><struct><var name='name'>\
# <string>Stefan Saasen</string></var><var name='custom_price'><number>126.0</number>\
# </var></struct></data></wddxPacket>"

== WDDX Data types

WDDX defines some data types which can not be mapped to native ruby classes. WDDX::Binary represents a binary object (which is in fact a BASE64 encoded String). WDDX::RecordSet represents a RecordSet with data rows an column meta information.

== Type mapping
The following table shows the data type mapping WDDX <=> Ruby.
WDDX Type Ruby Type
--------- ---------------------
String String
Number Numeric
Boolean TrueClass, FalseClass
Datetime Time
Null nil
Binary WDDX::Binary
Array Array
Struct Hash
Recordset WDDX::RecordSet

== Rails Plugin

You can add the wddx gem to your rails application to be able to serialize ActiveRecord objects to WDDX.

In config/environment.rb add:
require 'wddx'


a_ar_obj.to_wddx # => <wddxPacket...

== See

Homepage:: http://rubyforge.org/projects/wddx/
Blog:: http://juretta.com/
Bugtracker:: http://rubyforge.org/tracker/?group_id=2715
WDDX:: http://www.openwddx.org/