InformationWeek

An entire suite of protocols and programming tools, WAP is a framework that brings the Internet Web application programming model to handheld devices that have tiny displays, very low bandwidth connections, and extremely minimal storage and CPU resources. It isn't so much that WAP will enable the deployment of mobile applications that would be impossible otherwise. Rather, WAP offers a standard way to build these applications.

For businesses, WAP means there is now a global standard for developing mobile applications. The write-once, run-anywhere model of Web application development is now extended to any cell phone, handheld device, pager, or other properly connected device with a WAP browser. With estimates of more than 1 billion mobile subscribers by 2003, that's a compelling reach.

With handheld devices growing more powerful each year and wireless bandwidth similarly increasing, it might make more sense to use TCP/IP over wireless links instead of WAP. Devices already arriving are proving the viability of such solutions. However, there will always be a need for a very low resource solution, and WAP has, for the moment, no real competition.

The WAP model of programming is, in some ways, both simpler and more complex than the Internet model, and anyone looking to develop or deploy WAP applications needs to be aware of developer issues.

WAP is a standard created by the WAP Forum (www.wapforum.org), a consortium of companies that includes all the major wireless infrastructure companies, such as Ericsson, Motorola, and Nokia, as well as computer-industry vendors such as IBM, Intel, Microsoft, and Hewlett-Packard. At a cost of $27,500 per company to join, the WAP Forum represents an elite business proposition.

The WAP 1.0 specification was released in April 1998 (WAP 1.1 was released in June 1999), primarily on technology created by WAP Forum member Phone.com (formerly known as Unwired Planet). Phone.com, in turn, had relied heavily on the Internet Web application programming model. The result is that WAP protocols and developer languages have corresponding counterparts in the Internet domain.

The programming and display languages in the WAP environment are WMLscript, a lightweight scripting language that looks something like JavaScript, and the Wireless Markup Language (WML), an Extensible Markup Language (XML) derivative optimized for tiny displays.

In order to bridge the Internet and wireless environments-that is, to get content from a Web server on the Internet to a mobile device running a WAP browser-a WAP gateway is necessary. WAP gateways are also called WAP proxy servers, WAP proxy gateways, and Uplink servers, which refers to Phone.com's own WAP gateway product, the Up.Link Server.

A WAP gateway performs the needed protocol and format conversions to transmit content to a mobile device such as a cell phone. It's typically, but not necessarily, located in the network service provider's machine room.

If the whole world had already implemented WAP 1.1, life would be simpler for developers. Instead, WAP development comes complete with its own pre-WAP legacy browsers and gateways. Thus, developers working on WAP applications need to make sure they check their HTTP headers to retrieve the version of the WAP browser and the version of the WAP gateway that a cellular handset is using.

Depending on these versions, a somewhat different content syntax will need to be sent back to the handset. This is an unfortunate situation, but developers who create ap-plications and content for the Internet are used to doing the same thing for the various versions of Netscape and Internet Explorer browsers.

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