The Wireless Applications Protocol is the standard that will make surfing the Web and shopping from wireless devices commonplace. The WAP was developed by the WAP Forum, a consortium of device manufacturers, service providers, content providers, and application developers. The problem the WAP Forum was aiming to solve was that each of the device manufacturers and service providers were happily developing proprietary standards for delivering digital content through the air. The end result would have been consumers would be wedded to the wireless service provider that supported their phone. Wireless service providers also would have to deliver unique and appropriately formatted content to each different type of digital phone, and content providers would have to customize their content for each service provider''s network. A losing proposition all around. While some are already proclaiming the WAP dead, and soon to be replaced by 3G or the IMT-2000 standard being developed by the International Telecommunications Union, the reality is that the WAP is the worldwide standard that''s in place today. If you want to make your site viewable and your products purchasable by wireless users around the world, and you don''t want to go through a wireless data provider (see Wireless: Beyond the Hype), then you need to learn a bit about the WAP, the WAP Forum, and the architecture that underlies it.
Coming to Terms with Wireless
Wireless device - digital phone or personal digital assistant (PDA) that can connect to the Web without being plugged in.
Service provider - telecommunications company like Sprint PCS, MCI WorldCom, etc. that offers subscribers access to digital voice and data services.
Content provider - any Web site that makes its content available in a format compatible with wireless devices. |
WAP Forum Philosophy
The WAP Forum philosophy is simple: Build on existing standards. Whenever possible, WAP makes use of existing standards, thus not re-inventing the wheel. Where necessary, they make modifications to existing standards to make delivery to the unique interface limitations of wireless devices possible. For example, WAP is based on delivery of content using HTTP 1.1, just as is delivery of Web content to wired browsers. However, Wireless Transaction Protocol (WTP) replaces TCP, which isn''t well suited to the narrow-band communications of wireless devices. In many cases, a lighter, faster protocol that''s more supportive of the bandwidth constraints of wireless has been developed by WAP to replace the wired version of the comparable protocol. Wireless Constraints
Developing content for wireless devices requires rethinking the Web experience. Just as Windows and the Apple O/S (compared to DOS) represented a complete rethinking of the interaction between a user and the computer, wireless content developers need to begin from the ground up developing content for these strange new devices.
Wireless devices tend to have very little real estate available for viewing content - often as small as 14x7 characters. Wireless devices also tend to be monochromatic, so images don''t render well. There are no mice and the keyboards are difficult to use. Wireless devices tend to have limited CPU, memory, and battery life. Developers and designers need to find new, intuitive navigational techniques to overcome these constraints. Today the most common navigational technique on wireless is the list with drill-down capabilities.
Wireless User Behavior Differs From Wired User Behavior
Because of the constraints of using a wireless device and the relative inconvenience of performing any but the most straight forward, time-critical of tasks, wireless users won''t be expected to "surf the Web" in the traditional sense. More likely, wireless users are expected use their devices to execute small, specific tasks that they can take care of quickly, such as finding the time a movie''s showing, purchasing a CD, looking up sports scores or stock prices, etc.
Content developers need to develop with these motives in mind. Rather than just translating a content-rich site into WML (Wireless Markup Language), developers need to think in terms of:
- surgical access to their content,
- easy access to drilling down through the site from general information to detailed information, and
- how their sites navigate without the use of a mouse.
Service Providers
For service providers, the WAP is the best thing since sliced bread. Rather than having to develop their own tools for converting content into the myriad standards that device manufacturers might develop, they can be assured that all WAP-compliant tools and gateway software will work with all others. Customization is nearly eliminated. They can put their energy into offering better services to their subscribers, instead. When all phones are WAP-compliant, then service providers will be able to send content to any phones, eliminating the exclusive relationships that currently exist between device manufacturers and service providers. This means that wireless device owners won''t be tied to a single service provider, improving competition all around.
Wireless Markup Language (WML)
Wireless markup language is the HTML of wireless devices. It can be implemented in one of two ways. Sites can be written natively in WML, for delivery to all WAP-compliant devices, or sites can be written in XML, then XSL (XML Style Sheets) can be used to convert the XML into either WML or HTML, as requested by the browser. While developing in XML is a noble goal of the W3C, realistically, until wireless devices sport better screens and superior keyboards and pointing devices, sites should probably be developed separately for the two different access methods - not because of the different languages but because of the different interfaces.
WAP Protocol Stack
For those of you who want to understand the deep down, nitty-gritty of the WAP, here''s a quick summary. The WAP relies on stacked architecture, as does Unix, Windows NT, and most other newer technologies. Because wireless devices have limited memory, some layers of the stack have been offloaded to the WAP gateway (which is part of the service providers'' system). The layers, from top to bottom, are:
- the application layer, which relies on the Wireless Application Environment (WAE)
- the session layer, which relies on the Wireless Session Protocol (WSP)
- the transaction layer, which relies on the Wireless Transaction Protocol (WTP)
- the security layer, which relies on the Wireless Transport Layer Security (WLTS)
- the transport layer
- and the network layer.
This lightweight protocol stack minimizes bandwidth requirements, helping assure that a variety of networks can run WAP applications. WAP protocols conserve wireless bandwidth by reducing the number of communications that typically pass between the content provider and the browser. In HTTP/TCP/IP interactions, there are typically 17 messages back and forth in order display a page, (excluding DNS resolution, SSL, authentication, or cookies). In WSP/WTP/UDP interactions, the number has been reduced to 7. Since DNS resolution is handled by the WAP gateway, those additional communications don''t cut into the user''s bandwidth.
Resources
For an excellent overview of the WAP Protocol, please refer to the White Paper, Wireless Application Protocol, available from the WAP Forum site.
For more information about wireless applications and WAP, visit Thinkmobile.com
Alexis D. Gutzman is an E-commerce Technology Author and Consultant and author of The HTML 4 Bible, FrontPage 2000 Answers!, and ColdFusion 4 for Dummies. She can be reached at agutzman@internet.com
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