How WAP Works

WAP usesWireless Markup Language(WML), which includes the Handheld Device Markup Language (HDML) developed by Phone.com.

WML can also trace its roots toeXtensible Markup Language(XML). A markup language is a way of adding information to your content that tells the device receiving the content what to do with it. The best known markup language isHypertext Markup Language(HTML). Unlike HTML, WML is considered ameta language. Basically, this means that in addition to providing predefinedtags, WML lets you design your own markup language components. WAP also allows the use of standard Internetprotocolssuch asUDP,IPandXML.

There are three main reasons why wireless Internet needs the Wireless Application Protocol:

Most cell phones and Web-enabledPDAshavedata transfer ratesof 14.4 Kbps or less. Compare this to a typical 56 Kbpsmodem, acable modemor aDSLconnection. Most Web pages today are full of graphics that would take an unbearably long time to download at 14.4 Kbps. Wireless Internet content is typically text-based in order to solve this problem.

The relatively small size of theLCDon a cell phone or PDA presents another challenge. Most Web pages are designed for a resolution of 640x480pixels, which is fine if you are reading on adesktopor alaptop. The page simply does not fit on a wireless device'sdisplay, which might be 150x150 pixels. Also, the majority of wireless devices use monochrome screens. Pages are harder to read when font and background colors become similar shades of gray.

Navigationis another issue. You make your way through a Web page with points and clicks using amouse;但是,如果您使用的是无线device, you often use one hand to scroll keys.

WAP takes each of these limitations into account and provides a way to work with a typical wireless device.