An event is a change of the state of a trigger object. The
state change is defined as a change of a value of any
object parameter. In the MIM model, the Event element is
related to a change of a single parameter, but interaction
metadata can include many Event elements. The Event
element contains a set of preconditions that need to be
satisfied to trigger a particular interaction. These
preconditions include information about what has to
change to trigger an interaction, and where in 3D space the