Wireless Markup Language (WML) was designed to describe content and format for presenting data on limited-bandwidth devices such as cellular phones and pagers. In essence, WML, which is based on the content-tagging language XML, provides a tool to make Web pages accessible from handheld, wireless devices.
Rather than attempting to deliver the same Web page content you would see on a PC's Web browser, WML strips away much of the extra information found on pages coded with the Internet programming language HTML - especially graphics and animation. It presents mainly text-based information in a manner that's optimized and easily accessible for users of mobile devices, according to Roger Snyder, a senior product manager at Phone.com Inc. in Redwood City, Calif., one of the technology's leading proponents.
WML can be used in wireless devices to update electronic schedules, check inventory information from corporate intranets or present time-sensitive, discrete pieces of data such as stock quotes, weather reports, e-mail or calendar and appointment data.
Apart from helping developers present Web data in a better fashion, WML lets them optimize it for the slower connections of wireless devices. For instance, WML lets cellular phone users map frequently used Internet functions like looking up stock information to specific keys in the same manner that users can store frequently used telephone numbers.
Similarly, WML is telecommunications-aware and lets users do things such as switch between making calls and getting Internet information relatively easily, Snyder says.
Fueling a lot of the interest in technologies like these is the projected growth of wireless phone use, says Ken Hyers, an analyst at Cahners In-Stat Group in Newton, Mass.
"You are going to have 1 billion wireless phone users in 2002, while wireless penetration in the U.S will exceed 50% of the population it's a huge market," Hyers says.
The opportunity for vendors lies in making the Internet easier to access and interact with for such users, Hyers says.
"Given that we don't have much by way of [wireless] bandwidth today, we need some sort of a protocol that is very lightweight and suitable for moving information" from the Web to wireless devices, says Craig Mathias, an analyst at The Farpoint Group, a consultancy in Ashland, Mass.
WML's roots lie in efforts by Ericsson Inc. in Research Triangle Park, N.C.; Nokia Corp. in Irving, Texas; Motorola Inc. in Schaumburg, Ill.; and Phone.com to define a standard, widely accepted protocol for wireless communication with the Web.
These companies were responsible for defining Wireless Application Protocol (WAP), a set of rules for developing wireless Web applications. The companies decided to base WAP on Phone.com's Handheld Devices Markup Language (HDML) communications protocol. WML has since evolved from HDML.
The WAP (www.wapforum. org) Forum has grown to include more than 200 members, representing 95% of the global handheld market.
Because WML was designed for devices with small displays, its user interface is quite different from typical HTML pages. WML includes the following major functions:
Text and image support: For formatting and layout commands.
Deck/card organizational metaphor: Information in WML is organized into a collection of cards and decks. Cards specify one or more units of interaction (a menu, a screen of text or a text-entry field). Cards are grouped into decks.
A WML deck is similar to an HTML page in that it's identified by a Web address and is the unit of content transmission.
Support for explicitly managing the navigation between cards and decks: WML includes provisions for event handling, which may be used for navigation or executing scripts.
Rather than navigating through typical Web pages by clicking on links, users interact with the cards, moving forward or back through the deck. Another important difference is that while a single HTML page can contain multiple functions such as links and user-input capabilities, each WML card contains just one function. Each time a user presses a key, he moves to the next card in the deck.
If a Web site is to be accessible by WAP-enabled wireless devices, the site developers need to add an alternate version of each page, written in WML. The WML code specifies what data will be available to wireless devices.
While this process involves additional coding, Snyder says it's relatively painless. Most scripts and query tools used for retrieving and presenting data on HTML pages can be easily modified for use in a WML environment, he adds.
The real issue, though, is whether such a protocol will be needed in the long term, Mathias says.
Already, companies such as AvantGo Inc. in San Mateo, Calif., and ProxiNet Inc. in Emeryville, Calif., offer ways to mold standard HTML pages into formats suitable for wireless devices without requiring the creation of separate pages, says Jill House, an analyst at International Data Corp. in Framingham, Mass.
The continuing move to XML standards should make it easier to format Web pages for different devices, she says.
But for now, WML makes sense, especially "from the standpoint of optimizing [Web content]" for wireless phones, House says.
Wireless Markup Language is like the Internet programming language HTML. It delivers Internet content to small wireless devices, such as browser-equipped cellular phones and personal digital assistants, which typically have very small displays, slow CPUs, limited memory capacity, low bandwidth and restricted user-input capabilities.