XML:

• Extensible Markup Language
• A lightweight SGML designed for network use
• Addresses HTML's lack of evolvability
• Arbitrary elements can be defined (<STUDENT-NUMBER>, <PART-NO>, etc)
• Agreement achieved quickly - XML 1.0 became W3C Recommendation in Feb 1998
• Support from industry (SGML vendors, Microsoft, etc.)
• Support in latest versions of Web browsers