UsiXML


UsiXML is an XML-based markup language for defining user interfaces on computers.
UsiXML is a specification language for user interface design. It allows the designer to describe a user interface at different levels of abstraction. In other words, you can specify a UI in terms of: functionality, the object it manipulates, or in a more concrete way, user interface.
The UsiXML language is currently being submitted for a standardisation plan to the W3C.
Another work with the same purpose is UIML.

Tool support

There are plenty of tools that can be found for UsiXML.
They include: a translator from UsiXML specification to Flash, a tool for drawing/sketching user interfaces, a tool for task analysis.