Instrumental interaction is an extension of direct manipulation. It is based on the notion of interaction instrument, which acts as a mediator between the user and the manipulated object.
The model was used and further developed in the context of the CPN2000 project at University of Aarhus (Denmark) during my two-year visit in 1998-2000. CPN2000 is a graphical editor and simulator of colored Petri nets that uses marking menus, toolglasses and bimanual interaction techniques. Kurt Jensen's group at the University of Aarhus have continued the development of CPN2000 and distribute it under the name CPN/Tools. At the end of 2004, 1600 licences had been distributed worldwide.
Please see the following articles for details about the interaction model and the CPN2000 project: