XML , markup languages such as standard Generalized Markup Language(SGML) and Hypertext Markup Language(HTML) are also available.

SGML was released in 1980. It allows documents to describe their grammar by specifying the tag set used in the document and the structural relationship that these tags represent. This makes it possible to define individual formats for documents, handle large and complex documents, and manage large information repositories. However, SGML is complex and difficult for developers to master.

HTML was created by Tim Berners-Lee in 1989 as a simple and effective way of generating clear and readable documents. HTML enables you to create documents and Web pages that can be read by all web browsers . It uses a set of tags in conformance with the SGML specification.

The World Wide web consortium (W3C) developed XML to enable the expansion of Web technologies into the new domains of document processing and data interchange. XML is a subset of SGML. It is designed to ease data exchange over the Internet.  Though HTML and XML are markup languages, they have different purposes. HTML is used for data presentation, whereas XML is used for data description and definition.