What is XML?

• "The Extensible Markup Language (XML) is a subset of SGML that is completely described in this document [REC-xml-19980210]. Its goal is to enable generic SGML to be served, received, and processed on the Web in the way that is now possible with HTML. XML has been designed for ease of implementation and for interoperability with both SGML and HTML."
• XML Version 1.0 became an official recommendation on 10-Feb-98 (REC-xml-19980210, 32 pages)
• XML uses ISO 10646, the international standard 31-bit character repertoire which covers must human (and some non-human) written languages. This is currently congruent with Unicode.
• XML is a public format: it is not a proprietary development of any company.
• Think of XML as "SGML lite or SGML--, instead of HTML++"
• "XML will give Java something to do" - Jon Bosak, Sun Microsystems

An example of an XML file:

<?XML version="1.0"?> <ARTICLE>
<TITLE>The XML Files</TITLE>
<AUTHOR><LNAME>Dougherty</LNAME>
<FNAME>Dale</FNAME>
<EMAIL>dale@songline.com</EMAIL>
</AUTHOR>
<DATAPUB>97-05-16</DATEPUB>
<DESCRIPTION>
XML is the Extensible Markup Language. Instead of a fixed tagset such as HTML, XML documents can define their own tagsets for use in structuring content in Web documents.
</DESCRIPTION>
</ARTICLE>


Basic features:

• vendor independence (along with Java)
• user extensible (capable of being extended)
• complex structures
• validation
• human readability