25-08-2017, 09:32 PM
Wireless Application Protocol (WAP)
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An Introduction
The Wireless Application Protocol (WAP) is a new advanced intelligent
messaging service for digital mobile phones and other mobile terminals that will allow
you to see Internet content in special text format on special WAP-enabled mobile phones.
Enabling information access from handheld devices requires a deep understanding of
both technical and market issues that are unique to the wireless environment. The WAP
specification was developed by the industry’s best minds to address these issues.
Wireless devices represent the ultimate constrained computing device with limited CPU,
memory and battery life and a simple user interface. Wireless networks are constrained
by low bandwidth, high latency and unpredictable availability and stability. The WAP
specification addresses these issues by using the best of existing standards and
developing new extensions when needed. The WAP solution leverages the tremendous
investment in web servers, web development tools, web programmers and web
applications while solving the unique problems associated with the wireless domain. The
specification ensures that this solution is fast, reliable and secure. The WAP specification
is developed and supported by the wireless telecommunication community so that the
entire industry and its subscribers can benefit from a single, open specification.
The WAP forum
The WAP specification was developed by the WAP forum, a consortium
founded by the telecommunication giants Nokia, Ericsson, Phone.com and Motorola. The
WAP forum’s membership roster now includes computer industry heavyweights such as
Microsoft, Oracle, IBM and Intel along with several hundred other companies. The WAP
forum is an industry group dedicated to the goal of enabling sophisticated telephony and
information services on handheld wireless devices. The WAP forum has drafted a global
wireless protocol specification for all wireless networks and is contributing it to various
industry groups and standard bodies.
Goals of the WAP forum
The goals of the WAP forum are listed as follows.
• To bring Internet content and advanced data services to wireless phones and other
wireless terminals.
• To develop a global wireless protocol specification that works across all wireless
network technologies.
• To enable the creation of content and applications that scale across a wide range
of wireless bearer networks and device types, i.e. to maintain device and bearer
independence
• To embrace and extend existing standards and technology whenever possible and
appropriate
Ensure interoperability
Service providers must feel secure that their investments will yield benefits
in the future. They will not be able to do so until equipment and software offered by
different suppliers can be made to work together. The WAPspecification has been
designed to encourage easy, open interoperability between its key components. Any
solution component built to be compliant with the WAP specification can interoperate
with any other WAP-compliant component. Service providers can choose equipment and
software from multiple WAP-compliant vendors, selecting each piece of the solution that
is appropriate for the service provider’s particular needs.
Encourage and Foster Market Development
The WAP specification is designed to bring Internet access to the wireless
mass market. By building open specifications, and encouraging communication and
technical exchanges among the industry players, the WAP Forum has already begun to
open the wireless data market in new ways. Just over a year ago, the idea of a single
wireless data standard was unheard of, yet today the WAP specification is available to the
public, and dozens of companies are promoting this vision of the future. The revolution is
under way to bring information access to any handset, at a reasonable price and in an
easy to use form factor.
The Market Is Different
Bringing computing power to a wireless handset opens an extensive new
market for information access. This market is very different from the traditional desktop
or even the laptop market because the subscriber has a different set of needs and
expectations. Some of these differences include:
• Ease of use
• Market size
• Price sensitivity
• Usage patterns
• Essential tasks
WMLScript
Just as JavaScript allows client side processing for use with HTML,
WMLScript (Wireless Markup Language Script) is a client side script language for use
with WML. JavaScript can be used to make the pages more dynamic, and to perform
advanced mathematical calculations in HTML pages. WMLScript is very similar to
JavaScript and therefore easy to learn for those who have used that before. WMLScript is
actually based on ECMAScript (which is based on Netscape’s JavaScript language),
however it has been modified in places to support low bandwidth communications and
thin clients. WMLScript makes minimal demands on memory and CPU usage, while
omitting a number of functions that are not required from other scripting languages.
WMLScript is integrated with WML in a particularly flexible way for developers.
Server based computation means that several round trips to and from mobile
to server have to make in case of any interaction or computation. This is not very
desirable in case of low bandwidth systems. WMLScript allows code to be built into files
transferred to mobile client so that many of these round-trips can be eliminated. WML
script also allows developer to provide interactivity in WAP pages without taxing the
very valuable air interface. WMLScript functions can be called from within WML decks
or cards, although the function bodies themselves must be defined in separate
WMLScript files. Several predefined core libraries are available in WAP clients that
support WMLScript. These libraries provide basic string manipulation and mathematical
transforms, as well as functions specific to mobile phones. Just as with WML,
WMLScript can be binary encoded by the WAP Gateway/Proxy in order to minimise the
amount of data sent over the air.
WBMP
WBMP stands for Wireless BitMaP. It is the default picture format for WAP.
The current version of WBMP is called type 0. WBMPs are uncompressed, monochrome
black/white bitmaps intended for use in devices with small screens and narrow bandwidth
connection. The constraints when using WBMP are the small screen size, limited
graphics capabilities and the limited bandwidths available. As a thumb rule, a WBMP
should not be wider than 96 pixels and higher than 48 pixels at 72 dots per inch.
WTA
The Wireless Telephony Application (WTA) framework supports Wireless
Telephony Applications that interface with the in-device telephony related functions and
the network telephony infrastructure. The WTA framework extends the WAE framework
by adding:
• An interface from WTA-WML and WMLScript to a specific set of local,
telephony related, functions in the client. This interface is called the
“Wireless Telephony Application Interface” [WTAI].
• Network event handling. This means that events originating from the mobile
network could be detected by the WTA user-agent and actions in response to
the events could be defined.
• A repository, which is a storage container, used by the WTA user-agent, that
persistently stores content that executes WTA services.
• A model for WTA user-agent state and WTA context management.