The Third Wave: Power Through Combination | XML, Web Services, and the Data Revolution


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	XML, Web Services, and the Data Revolution By Frank P. Coyle
	Table of Contents

	Chapter 3. XML in Practice

XML's simplicity opens it up to combination.

XML's third wave of application comes from XML's ability to combine with other technologies and give rise to new technologies that go beyond their constituent parts . Figure 3.7 illustrates XML's use in conjunction with other technologies. Systems engineers have long known that to understand and manage a working system requires an understanding of the dynamics that emerge when individual components interact, behaviors that are different from that those associated with individual parts.

Figure 3.7. The third wave of XML applications: protocols for distributed interaction.

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XML protocols leverage the power of combination.

XML's emergence as a protocol language falls into this category. Because XML has limited itself to data description, it isn't constrained by programming language, platform, or transport considerations. It's open to combination with any number of different technologies. It is this combinatoric capability of XML that has propelled it into the world of protocols and distributed computing. Leveraging the power of HTTP and TCP/IP to deliver data anywhere across the Internet, XML in combination with HTTP (and other transport protocols) has been the basis for two important protocols: XML Remote Procedure Call (XML-RPC) and Simple Object Access Protocol (SOAP).

Although we will cover XML-RPC and SOAP in detail in Chapter 4, it's helpful to look at how XML protocols are affecting XML's acceptance and use. XML protocols such as XML-RPC and SOAP are among the drivers behind a new model of distributed computing based on loosely coupled Web components and giving rise to the emergence of Web services (which we explore in Chapter 5). This use of XML across a broad spectrum of applications has created a groundswell of interest from both corporations and government. No longer viewed as an experimental emerging technology, XML is now accepted as a key technology, not just for data storage and exchange, but as a building block, underpinning the protocols that move data across networks. As we explore in the next section, this multifaceted use of XML has been one of the drivers of the British government's strategic vision for its next -century information system.

The British Government GovTalk Initiative

GovTalk is the name given to the British government initiative to use XML as the basis for exchanging information among government systems, between the government and its citizens and businesses worldwide, and between the UK and foreign governments . It is an initiative led by the Cabinet Office, designed to get UK public-sector organizations and private-sector companies to work together in agreeing on XML schemas and providing associated support to the UK public sector.

The main thrust of the specification has been to adopt the Internet and Web standards for all government systems. At the core of the standards effort is the strategic decision to adopt XML as the main standard for data integration. This strategy includes using XML schemas throughout the public sector based on agreed-upon governmental data standards.

Shaping this effort have been three important policy decisions:

Internet alignment: The universal adoption of common standards used on the Internet and World Wide Web for all public-sector information systems
XML: The primary standard for data integration and presentation tools for all public sector systems
Web browser as GUI: All public information systems will be accessible through browser-based technology. Other interfaces are permitted but only after browser support has been implemented.

Figure 3.8 demonstrates how GovTalk provides implementation support through the availability of a central XML schema repository that can be reused throughout the public sector to reduce the costs and risks of developing data interchange systems. Before defining schemas for their data, ministries are encouraged to explore the online repository for relevant XML schema definitions, reports on best practices, and toolkits for developing interfaces and converting existing data.

Figure 3.8. The British Government's GovTalk initiative uses XML as the basis for data exchange across all aspects of government information technology. XML Schemas will be used to define data for all government ministries, and XML protocols will be used to exchange information between ministries.

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Like ZwiftBooks, the British Government has found XML- related technologies useful to support interoperability and integration. Government policy is now officially to use XML and XML Schema for data integration; Unified Modeling Language, Resource Description Framework, and XML for data modeling; and the description language XSLT for data transformation.

GovTalk is also now being used for wide consultation on a number of other e-government frameworks and documents. It is intended to make adoption of XML-based policies and standards simple, attractive, and cost effective.


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