Wireless Markup Language

Wireless Markup Language (WML) is an HTML-variant markup language as part of the Wireless Application Protocol, an attempt to reinvent the Web for the bandwidth, CPU, and memory limitations of wireless networks and mobile devices. WAP existed around the turn of the millennium, and flopped within a few years.

Curiously, the official site's hub page for WAP specifications links to password-protected documents. However, a slightly older copy can be found by search engine.

WML is accompanied by a scripting language called WMLScript. There is also a compact binary variant based on the WAP Binary XML Content Format.

Description
WML is XML-based with an overall document structure that looks like this:

 <!DOCTYPE WML PUBLIC "-//WAPFORUM//DTD WML 1.0//EN" "http://www.wapforum.org/DTD/wml.xml">   ...     ...    

A WML document is structured as a deck of navigable cards. One card is visible at a time, and may contain text and form input fields. Each card has an associated "action," which may involve navigation to other cards and submission of form data over the network.

WML also supports variable substitution for some reason. Variables are declared with the  element and invoked using a dollar sign, e.g..