VBI (and, in general, PUls) can be categorized into two aspects: control and awareness. Control is explicit communication to the system e.g, put that object there. Awareness, picking up information about the subject without an explicit attempt to communicate, gives context to an application(or to a PUI). The system may or may not change its behavior based on this information. For example, a system may decide to stop all unnecessary background processes when it sees me enter the room- not because of an explicit command I issues, but because of a change in its context. Current computer interfaces have little or no concept of awareness. While many research efforts emphasize VBI for control, it is likely that VBI for awareness will be more useful in the long run.