Extensible Markup Language (XML) belongs to the Markup Language family just like HTML or WML. But with XML, we can define our own custom tags. For example :
<UPN><Informatics>… .. </Informatics></UPN>
In XML, to explain whether a tag is valid or not, we can use DTD (Document Type Definition). The DTD also describes the structure of the XML document. Then to explain the meanings of the tags created, a stylesheet can be used, namely XSL (Extensible Stylesheet Language). XSL consists of three parts and each part has its own recommendations from the W3C, namely: Xpath (XML Path Language), a language for indicating a part of an XML document. XSLT (XSL Transformation), a language for transforming an XML document into another document. XSL, namely XSLT plus a collection of explanations about formatting objects and formatting properties.
