The Internet Encyclopedia (Volume 3)

P1: IML

Cassel WL040/Bidgoli-Vol III-Ch-65 September 15, 2003 8:52 Char Count= 0

814 WIRELESSAPPLICATIONPROTOCOL(WAP)

Figure 11: Wireless network access environment (Wireless Application Protocol, 2000).©c 2000 Wireless

Application Protocol Forum, Ltd. Reprinted with permission.

application and can rely on existing techniques. Control

in the push environment is left to establishing trust be-

tween the client and the push proxy. The push proxy uses

existing techniques to ensure security with data-providing

servers.

The extra step involved is the use of a gateway be-

tween the client and the information provider. This intro-

duces another factor into consideration of overall secu-

rity. WTLS addresses security between the device and this

pull gateway. Existing Web security mechanisms are used

to provide security between the gateway and the service

and/or data provider.

Design Considerations

Design considerations have figured in several parts of this

chapter. The following points summarize the major issues.

Considering Speed

Bandwidth is still much lower for handheld wireless de-

vices than for wired Web connections. As a result, bits

that do not contribute to the user achieving a desired re-

sult will not be well regarded. Recent advances in design

of engaging and entertaining Web pages will not serve this

population. The application developer must focus on get-

ting the message across in as few words, symbols, and

images as possible.

There is another consideration related to speed, be-

sides the limitation of bandwidth. It is important to con-

sider where and how these devices are likely to be used.

Often the device user is walking or taking time out from a

meeting or other activity. He or she is not seated com-

fortably in his or her office or living room. The other

constraints on these systems mean they are not generally

the first choice for casual browsing. The user wants some

information and wants it now. This is not the environment

for enticing the visitor to explore the wonders of the site.

A prompt and pointed response to a request will suit the

user’s needs and bring him or her back another time.

The Small Screen

The small screen has been mentioned a number of times

and an example is shown in the illustrations. Although

bandwidth and resolution on the screen will improve, the

screen will not get larger, because smallness is a prized

feature of many WAP-enabled devices. Some devices, such

as PDAs, have larger screens than others. However, appli-

cation developers must assume that the screen is small,

often does not display color, and may be viewed in diffi-

cult lighting environments. Interaction must be designed

for ease of use under these circumstances.

Navigation

Because of the small screen, the basic model of a “doc-

ument” becomes a deck of cards. Each card contains a

small amount of information and may contain a link to

another card in the same deck or in a different deck. WAP

provides all the power of the Web to reach sites and to

initiate processes on remote services. However, the re-

sults of those server processes and the information on the

Web pages will be constrained by the presentation envi-

ronment. Each WAP client must have a way to interact

with a specified set of events triggered by user actions. The

way these are made available and the ease of user access

will vary. An accept button and a button that goes back

to the previous card are the most dependable constants.

Presenting navigation options as links in a list allows the

user to scroll through the choices and accept the most

appropriate one.