Summary

When people discuss XML, it is sometimes unclear exactly what they are referring to. XML consists of a growing number of architectural components that we will describe in this chapter. We start off with a description of the design goals, and how these goals influenced XML's development. Understanding these design goals gives data managers insight into how XML is different, and how it has avoided some of the drawbacks associated with other technologies. Next in a section called “What XML Is Not,” we further explore the most common issue that have caused confusion about XML. The next section describes the overall organization of the components, and how they evolved. The rest of the chapter is devoted to individual descriptions of the various components. Covered in this chapter are DTD, XML Schema, DOM, XPath, XLink, XPointer, XSL, XSLT, RDF, SOAP, WSDL, UDDI, and ADML—a veritable alphabet soup of XML acronyms. At the end of the chapter, you will have a more complete picture of the constellation of components, and you will understand what is meant when “XML” is referred to in various contexts, along with a solid list of capabilities it brings to the table.