Wikipedia
XForms is an XML format used for collecting inputs from web forms. XForms was designed to be the next generation of HTML / XHTML forms, but is generic enough that it can also be used in a standalone manner or with presentation languages other than XHTML to describe a user interface and a set of common data manipulation tasks.
XForms 1.0 (Third Edition) was published on 29 October 2007. The original XForms specification became an official W3C Recommendation on 14 October 2003, while XForms 1.1, which introduced a number of improvements, reached the same status on 20 October 2009.
XForms is a GUI toolkit based on Xlib for the X Window System. It features a rich set of objects, such as buttons, scrollbars, and menus etc. In addition, the library is extensible and new objects can easily be created and added to the library.
Distributed under the GNU Lesser General Public License, XForms is a free software.
XForms was based on the Forms Library by Mark Overmars, converted from IRIS GL (a precursor to OpenGL that also included calls to create windows and manage events) to X11. A similar conversion was used to make the first versions of fltk, so all these toolkits are distantly related.
The toolkit was originally used by the Xfce desktop environment before the switch to the GTK+ toolkit.