XML, Web Services, and the Data Revolution

By Frank  P.  Coyle

XML's strength is its simplicity. Its primary focus is data. All the rest ”formatting, display, type checking, manipulation, search, and query ”are associated with one of the family of technologies that surround an XML core. In this chapter we examine the XML core and its surrounding technologies. At the heart are XML and namespaces , which together provide a foundation for unambiguously delivering structured documents across the Web. Moving beyond the core we find a collection of technologies for presentation, data typing, and manipulation.

In regard to presentation, we look at cascading style sheets (CSS), Extensible Hypertext Markup Language (XHTML), Extensible Style sheet Language (XSL) formatting, and VoiceXML, which provide options for delivering XML to a variety of devices in a number of different formats. For data typing we look at document type definitions (DTDs) and XML Schema . For client- and server-side manipulation and transformation, we examine XSL Transformations (XSLT), XPath , XLink , and XQuery , technologies for transforming, navigating, and extracting XML. Finally, to round out our discussion, we examine the XML Information Set (InfoSet) and its metadata capabilities that provide a basis for XML technologies to work together with a common semantic meaning, and then look at the Resource Description Framework (RDF) as the basis for what is referred to as the Semantic Web .