An Overview Of Distributed Data For The Web; Wddx Components - MACROMEDIA COLDFUSION 4.5-DEVELOPING WEB Develop Manual

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The best source of information about WDDX is http://www.wddx.org/. This site,
sponsored by Allaire Corporation, offers a free download of the WDDX SDK and a
number of resources, including a WDDX FAQ and a developer forum.

An Overview of Distributed Data for the Web

Web Distributed Data Exchange (WDDX) is an Extensible Markup Language (XML)
vocabulary for describing complex data structures such as arrays, associative arrays,
and recordsets in a generic fashion so they can be moved between different
application server platforms and between application servers and browsers using only
HTTP . Target platforms for WDDX include ColdFusion, Active Server Pages, JavaScript,
Perl, Java, Python, and COM.
Unlike other approaches to creating XML-based generic distributed object systems for
the Web, WDDX is not designed as an analog of traditional object programming
languages. These approaches use XML as a generic descriptor for initiating remote
procedure calls between different object frameworks. This is a valuable approach to
the problem of using traditional object-based applications to the Internet, but it is
more useful as a bridge between different programming paradigms than it is as a Web-
native methodology for distributing structured data between application.
There are several problems with merging the distributed object model of computing
with the Internet. Primarily, this model was designed with a completely different vision
of what general internetworking would look like. Instead of the "dumb and
disconnected" model of HTTP , distributed computing was built on the assumption of
rich network services that would allow resources on remote machines to act like local
components. These services allow an application on one system to find, invoke, and
maintain state with objects on a remote system. Communication between objects on
remote systems uses an efficient, special-purpose wire protocol.
But these services are a barrier to development in the disconnected world. At the most
fundamental level, the wire protocols of Distributed COM and CORBA are blocked by
most Web firewall software. But the largest barrier is that client-server oriented
distributed computing frameworks impose a development methodology that is
radically different from that of the Web. This methodology excludes the vast majority
of developers building Web applications whose main tools are tag-based markup
languages and scripting. While WDDX will work with systems that support component
object development paradigms, there is a large set of applications that can benefit
from the general characteristics of a distributed data system without the client-server
overhead.

WDDX Components

The core of WDDX is the XML vocabulary, and a set of components for each of the
target platforms to serialize and de-serialize data into the appropriate data structure
and a document type definition (DTD) that describes the structure of standard data
types. Functionally, this creates a way to move data, its associated data types and
Developing Web Applications with ColdFusion