63. XML

XML, or Extensible Markup Language, is a dialect of SGML. It was developed under the direction of the W3C?s XML Working Group in 1996 with the following design goals in mind. XML shall be straightforwardly usable over the Internet. XML shall support a wide variety of applications. XML shall be compatible with SGML. It shall be easy to write programs which process XML documents. The number of optional features in XML is to be kept to the absolute minimum, ideally zero.

XML documents should be human-legible and reasonably clear. The XML design should be prepared quickly. The design of XML shall be formal and concise. XML documents shall be easy to create. Terseness in XML markup is of minimal importance. The W3C believes that XML will play an increasingly important role in the exchange of a wide variety of data on the Web by Enabling internationalized media-independent electronic publishing.

Allowing industries to define platform-independent protocols for the exchange of data, especially the data of electronic commerce Delivering information to user agents in a form that allows automatic processing after receipt Making it easy for people to process data using inexpensive software Allowing people to display information the way they want it Providing metadata -- data about information -- which will help people find information and help information producers and consumers find each other.

XML is not a new form of HTML, nor is it a replacement for SGML. XML is an abbreviated version of SGML that makes it easier to define document types and easier for programmers to write applications to handle those documents. Since HTML is a subset of SGML, XML and HTML are somewhat similar in terms of appearance and of a limited amount of functionality.