UsiXML (USer Interface eXtensible Markup Language) 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 (task analysis), the object it manipulates, or in a more concrete way, user interface.
[2] They include: a translator from UsiXML specification to Flash (FlashiXML), a tool for drawing/sketching user interfaces (SketchiXML), a tool for task analysis (idealXML).