WAP: The Web for Cellphones and PDAs (4/4) - exploring XML

Bridging the gap

The two worlds of telecom network and Internet can be quite easily connected via a specialized WAP gateway:

Client	Gateway	Server
WML WMLScript Libraries	WML Encoder WMLScript Encoder Protocol Adapters	CGIs, servlets, etc. for producing WML and WMLScript

Client

Gateway

Server

WML
WMLScript
Libraries

WML Encoder
WMLScript Encoder
Protocol Adapters

CGIs, servlets, etc.
for producing
WML and WMLScript

The process resembles the way Web pages are served up:

The user presses a phone key related to a particular URL

The client sends the URL to the gateway using WAP protocols

The gateway translates the WAP request into an HTTP request

The Web server handles the request just like any other HTTP request. It either returns WML or HTML back to the gateway using standard Web techniques such as CGI or servlets.

The gateway receives the response on behalf of the client. HTML gets transcoded to WML if necessary, and WML and WMLScript get encoded into byte code that is then passed back to the client

The client receives the response in WML byte code and displays the first card in the deck to the user.

WAP browser war ahead?

While the WAP standard was quickly criticized as being too restrictive in its assumptions for device capabilities, it promises a relatively interoperable platform (in the current WAP version 1.1) that all major cellphone manufacturers agree on and adhere to. Glitches in the first implementations that caused different phones to recognize different mime types and image formats seem to be largely resolved. Unfortunately, this was before the PDA and PC worlds developed a stronger interest in the subject.

Now more WAP browser implementations with differing extensions and improvements are starting to appear, including from one company (or soon to be two companies) from Redmond, Washington. Arguments whether WML should be replaced with HTML, or XHMTL are being exchanged. Microsoft's micro-browser allegedly supports both, once again embracing and extending, as well as bloating the software into a mega-browser. Ring any bells? Those who do not learn from history are condemned to repeat it... But then again, Nokia does not look like it could become easily "Netscaped". You cross-browser experts out there, a new playing field seems to be emerging for you!