Entity is an application framework built around XML. The core of Entity is
actually an engine that allows you to create objects out of XML by supplying
methods for creation, attribute-setting, and destruction of XML nodes in a
tree.

This design allows you to create tags in XML which can be used to represent
pretty much any object.  We have used this to create a set of tags for the GTK+
toolkit, allowing you to create graphical applications using XML, and an
embedded scripting language.

Any scripting language supported by Entity can be used to change the XML tree
during runtime, and the changes are immediately reflected in the rendered
representation of the XML.  Using XML for the user interface, data storage, and
code of an application allows you to easily implement configuration, saving,
and undo.

The interface for creating UIs and programming in Entity is quite intuitive and
allows for rapid application development.  Entity currently supports Perl,
Python, TCL, Javascript, and C for doing runtime XML creation and modification.

WWW: http://entity.sourceforge.net/