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30.5. Examples of XML Technology

With XML's ability to allow customized tagging systems, it's not surprising that it is finding a wide variety of uses. It has already made a big impact on the Internet since its formal introduction in 1998. This section takes a look at just a few of the ways XML is being put to work.

30.5.1. Standard XML Languages

The World Wide Web Consortium monitors standard XML applications (languages written according to the rules of XML) that have an impact on how media is presented over the Web, thus changing the Web's capabilities. In fact, virtually all new web-related technologies and languages developed by the W3C follow the rules of XML. This section looks at the more prominent developments.

30.5.1.2. Scalable Vector Graphics (SVG)

XML has typically been used to define the structure of text elements within a document; however, many groups are working on ways in which it could be used to define graphical information as well. The W3C is developing the Scalable Vector Graphic (SVG) standard. According to the W3C:

SVG is a language for describing two-dimensional graphics in XML. SVG allows for three types of graphic objects: vector graphic shapes (e.g., paths consisting of straight lines and curves), images and text. Graphical objects can be grouped, styled, transformed and composited into previously rendered objects. Text can be in any XML namespace suitable to the application, which enhances searchability and accessibility of the SVG graphics. The feature set includes nested transformations, clipping paths, alpha masks, filter effects, template objects and extensibility.

The following sample SVG code (taken from the W3C Recommendation) creates an SVG document fragment that contains a red circle with a blue outline (stroke):

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 20001102//EN" 
"http://www.w3.org/TR/2000/CR-SVG-20001102/DTD/svg-20001102.dtd">
<svg width="12cm" height="4cm">
<desc>Example circle01 - circle expressed in physical units</desc>

<circle cx="6cm" cy="2cm" r="1cm"
        style="fill:red; stroke:blue; stroke-width:0.1cm" />
</svg>

The SVG standard provides ways to describe paths, fills, a variety of shapes, special filters, text, and basic animation.

Adobe offers tools for both creating and viewing SVG files. The drawing program Illustrator 9 can now export .svg files directly. Adobe's SVG Viewer is a browser plug-in available for Navigator and Internet Explorer 4 and higher for Windows and Macintosh that allows SVG files to display in the browser window.

For more information on SVG, see the W3C pages at http://www.w3.org/Graphics/SVG/.

30.5.2. Other XML Applications

Some XML technologies serve a specific community, as the Chemical Markup Language serves the scientific community, but these technologies are often of limited interest to most publishers. Others are so specific that they serve only a particular intranet of a single business.

XML is poised to become a major player on the Internet. Companies are excited by the technology and have invested large amounts of time and money in its development.

The following are just a few of the ways XML is being implemented today.

Wireless Markup Language (WML)

WML is an XML application for marking up documents to be delivered to handheld devices such as PDAs and cell phones. It is discussed in more detail in Chapter 32, "WAP and WML".

DocBook

DocBook is a DTD for technical publications and software documentation. DocBook is officially maintained by the DocBook Technical Committee of OASIS, and you can find the official home page located at http://www.oasis-open.org/committees/docbook/.

Chemical Markup Language (CML)

CML is used for managing and presenting molecular and technical information over a network. For more information, see http://www.xml-cml.org.

Open Financial Exchange (OFX)

OFX is a joint project of Microsoft, Intuit, and Checkfree. It is an XML application for describing financial transactions that take place over the Internet. For more information, see http://www.ofx.net/ofx/default.asp.

Simple Object Access Protocol (SOAP)

This technology, developed by Microsoft, DevelopMentor, and Userland Software, uses the ubiquitous support for XML and HTTP to provide a way for applications to talk to each other over the Internet, regardless of platform and through firewalls. For more information, start with this article by Microsoft: http://www.microsoft.com/mind/0100/soap/soap.asp. For technical details, see the W3C notes at http://www.w3.org/TR/2000/NOTE-SOAP-20000508/.



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