| XML is not just one technology or specification but a family of technologies that work together to enable an infrastructure for describing, presenting, and manipulating XML-based data. At the core is XML and the XML namespaces Recommendations, which form the basis for defining data unambiguously. For description, there are DTDs and XML Schema, which provide a way to describe the structure and content of XML documents. These schema can be used by both clients and servers to determine document validity, thereby reducing the need for specialized programmatic document checking. For display, there are a variety of technologies including XForms, VoiceXML, and XHTML that offer modular options for working with many different kinds of user interfaces. For XML manipulation and transformation, XSLT is a key technology supported by XLink, XPath, and XQuery. Finally, InfoSet provides a mechanism that allows different XML technologies to work together, and RDF opens up the possibility of an expanding, evolving Semantic Web. While these topics do not by any means cover all the technologies in the XML family, they provide a good starting point to begin to understand the scope and power of XML and how it can be applied to a variety of problems.  |
