Patterns: Implementing Self-Service in an SOA Environment

Chapter 6. Technology options 111

Some HTML 4 features have been found inappropriate for non-desktop devices,

so extending and building on XHTML Basic will help to bridge that gap.

XForms

XForms is W3C’s specification for Web forms that can be used with desktop

computers, hand-held devices, and so forth. The disadvantage of the HTML Web

forms is that there is no separation of purpose from presentation. XForms

separates the data and logic of a form from its presentation. Also, XForms are

device-independent.

XForms uses XML for transporting the data that is displayed on the form and the

data that is submitted from the form. HTML is used for the data display.

Currently, the main issue with XForms is that it is still an emerging technology, so

browser and server support is not yet standard.

6.2.2 Mobile clients

Mobile clients include wireless devices such as phones, pagers, and PDAs. The

challenges these devices bring as Web clients are based primarily on the very

limited computer resources of the supporting platform. The goal, however, is to

overcome these limitations to provide access to information and application

services from anywhere by leveraging and extending the existing Web server

architectures.

Devices

Mobile devices include wireless desktop PCs, WAP devices, i-mode devices,

PDAs, and Phone w/Voice. PDA devices cannot run the major operating systems

that run on desktop PCs and consequently there are various mobile

device-specific platforms. Palm devices use Palm-OS. WinCE/PocketPC devices

use a version of Microsoft Windows called Windows CE.

Voice

Voice-enabled applications allow for a hands-free user experience

unencumbered by the limitations of computer interface controls.

Voice technology fall into two categories: Those that recognize speech and those

that generate speech. The ability to recognize human voice by computers is

called

Automatic Speech Recognition (ASR). The ability to generate speech from

written text is called

speech synthesis or Text-to-Speech (TTS).

112 Patterns: Implementing Self-Service in an SOA Environment

Architecture

Support for mobile clients impacts the runtime topology and therefore must be

designed and implemented using best practices for system architecture. The

good news is that any past investment in Web architecture to support

Internet-based applications can be extended to support mobile clients.

A Wireless Application Protocol (WAP) gateway is used between the mobile

client device and the Web server. The gateway translates requests from the

wireless protocol into HTTP requests and, conversely, converts HTTP requests

into the appropriate device format.

WAP

WAP is the Wireless Application Protocol. This is the standard for the

presentation and delivery of information to wireless devices, which are platform,

device, and network neutral. The goal of this protocol is to provide a platform for

global, secure access through mobile phones, pagers, and other wireless

devices.

Microbrowser

WAP microbrowsers run on mobile clients. They are responsible for the display

of Web pages written in WML and can execute WMLScripts. These play the

same role as HTML browsers that run on a PC.

WML

The Wireless Markup Language (WML) is based on XML and HTML 4.0 to fit

small hand-held devices. It is a tag-based language that handles formatting static

text and images, can accept data input, and can follow hyperlinks.

WMLScript

This is the companion language to WML, in the same way as JavaScript is a

companion language to HTML. WMLScript allows for procedural programming

such as loops, conditional, and event handling. It has been optimized for a small

memory footprint and small devices. This language is derived from JavaScript.

Bluetooth

Bluetooth is a set of technical specifications for low-range (up to 30 feet) wireless

devices that define standards such as power use and radio frequency. The goal

of this technology is to connect a wide range of computing and

telecommunication devices easily and simply in a peer-to-peer manner.