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Chapter 11. XML and Web Services > XML for Data Exchange - Pg. 140

XML and Web Services 140 The use of XML can solve these problems by stronger separation of form and content. Content is best expressed in domain-specific XML, whereas form will be handled by transformations and stylesheets for different purposes. At this writing, we're still in the transition from a fragmented HTML universe to a unified XML universe. On the content side, the W3C has reformulated HTML 4.01 into strict XML as XHTML 1.0. This doesn't add new capabilities, but the regularity of XML and the availability of processing tools will greatly simplify content processing. For formatting and rendering, the use of XHTML immediately provides a baseline parity with HTML, and the use of cascading style sheets provides better control over rendering. XSLT provides transformations from domain-specific vocabularies to XHTML, and the forthcoming XSL Formatting Objects recommendation will provide precise control over rendering to multiple devices. XML for Data Exchange In the same way that ASCII unified the representation of computer data, XML is unifying the repre- sentation of structured computer information. There are many reasons for this. · XML is soothing. Competitive groups find it possible to agree on standardized document formats for domain- specific information, either because XML isn't viewed as anyone's proprietary baliwick or be- cause it is flexible enough to be inclusive. · XML lets general-purpose software handle variant data. XML is designed to carry many different document formats in a uniform way. Software that processes XML can therefore handle multiple document types without modification while still being able to modify and process the parts of documents that they understand. The alternative approaches require opaque objects or high degrees of complexity. · XML simplifies application architecture. Many business applications require communication, processing, and storage of many different document types. The use of XML for all of these functions provides a uniform framework for information that both simplifies the application architecture and increases the degree of reuse of code. In this section we examine three efforts that use XML for business purposes: the Open Applications Group, Inc. (OAGI), ebXML, and RosettaNet. OAGI The Open Applications Group, Inc. (OAGI) has taken on the problem of developing XML business document type definitions for common business activities. To date, more than 200 Business Object Documents (BODs) are available. Each BOD is an XML document containing a control area that is standard and a data area that varies according to the type of the document. The vision and objective of the OAGI, shown in Figure 11-4, is simple: if applications all use a common set of business documents, application integration can be turned from an O ( n 2 ) prob- lem 4 to an O ( n ) problem, greatly reducing the effort. 4 The notation O(n 2 ) means that the cost of solving a problem grows with the square of the size of the problem, as measured by n (bad). Similarly, the notation O ( n ) means that the cost of solving a problem grows linearly with the size of the problem (good).