Wireless Application Protocol (WAP) is the de facto standard for providing Internet communications and advanced telephony-based services over digital mobile telephones, pagers, personal digital assistants (PDAs), and other wireless terminals. WAP is an open, global standard that empowers users of mobile telephones and wireless devices to securely access and instantly react with Internet information and services.
This single-industry, agreed-upon standard for wireless application interoperability uses an XML-compliant markup language called WML (Wireless Markup Language). The advantage of WML is that it provides a path for application developers as well as content providers to develop and deliver Web-based services. The WML user interface is a WAP microbrowser that maps into mobile phones and other wireless devices. Devices using WAP-based microbrowsers can access an array of innovative value-added services.
The basic concept of WAP is to specify the network server, the mobile telephone software, and the communications between them. Communication is established between the mobile handset (client) and a gateway that serves as the gateway to the Internet. The gateway supports protocol and format conversion between a network application server, enabling communication with a WAP-enabled handset or client.
WAP is designed to function over any wireless network, including CDPD, CDMA, GSM, PDC, Mobitex, and others. An application server on the Internet provides the information or data desired by the client while the network serves as the bearer for the data.
Microbrowser firmware is embedded into the mobile phone and the developer must be able to support that version of the microbrowser. However, because each manufacturer is different, there are subtleties that the developer must be able to support for each handset. Further, the programming language used to develop applications (WML or HTML) may have variants when deployed in the Asian market, where slightly different versions of these programming languages are used. This forces developers to be conversant in four versions of the markup language and to design their applications to interface with each of these language variants.
Design differences in the handset create additional problems for the developer because screen space varies, forcing the application designer to work toward the lowest common denominator. Because present-day WAP telephones are slow and do not always respond as expected, software applications may not perform as designed. This creates additional design problems affecting security and user privacy issues.
WAP specification is unique because it defines an open standard architecture and set of protocols intended to facilitate wireless Internet access. It provides solutions for problems not solved by other standards bodies (e.g., W3C, ETSI, TIS, IETF, etc.) and serves as a catalyst for wireless development and standardization. The specification's key elements include a definition of the WAP programming model, which is based on the existing World Wide Web programming model. This serves to benefit the developer community because it provides a familiar programming model, an established architecture, and the ability to leverage existing tools (i.e., Web servers, XML tools, etc.). A markup language adhering to XML standards is designed to enable powerful applications within the constraints and limitations of handheld devices. WML and WML Script do not assume the availability of a QWERTY keyboard or mouse for user input. Unlike the flat structure of HTML documents, WML documents are divided into a set of well-defined units of user interaction.
Another key element is the specification for a microbrowser in the wireless terminal that controls the user interface and is analogous to a standard Web browser. This specification defines how WML and WML Script should be interpreted in the handset and presented to the user.
In addition to the above, there is a lightweight protocol stack to minimize bandwidth requirements, guaranteeing that a variety of wireless networks can run WAP applications, a framework for Wireless Telephony Applications (WTA) that allows access to telephony functionality such as call control, phone book access, and messaging within WML Script applets. This allows the operator to develop secure telephony applications integrated into WML/WML Scripts.