This paper presents our research on the Interaction Techniques Markup Language (InTml). Our final goal in this work is to find ways to evolve and fit virtual reality (VR) applications over heterogeneous hardware platforms, a process we call retargeting. Toward this goal, we have developed a hardware-independent, component-based, formal model that describes the execution of VR applications; an XML language for describing complex and implementation-independent VR applications; a methodology for InTml-based development; a manual way to isolate and replace interaction techniques as a contribution to VR retargeting; and a set of tools for development support. This paper describes these topics and states future directions of our research.