XML includes a family of technologies standardized by the W3C supporting device- and implementation-independent mechanisms for representing data. In raw XML, all data is represented as strings, though the data itself may represent dates, numbers, binary or any other type of information.
Sitecore stores XML using the UTF-8 character set and uses the fundamental XML constructs of XSL, XPath and XHTML. XSL is generally used for rendering content from Sitecore’s XML repository into various other formats for different devices such as browsers, and XPath is used as a limited query language in XSL to index into the XML content repository. XHTML is a markup language generally used for content, much like HTML but enforcing additional rules.
Both XSL and XHTML are XML dialects – syntaxes implemented in XML. In other words, XSL and XHTML data is XML data which conforms to various rules implemented in those XML dialects. Complete descriptions of these technologies are beyond the scope of this document as they are provided by a number of existing resources such as http://www.w3.org/XML, http://www.w3.org/Style/XSL, http://www.w3.org/TR/xpath and http://www.w3.org/TR/xhtml1/.