What is augmented reality? Rather than the subject of a dorm bull session, that was a valid question at the Augmented Reality Event, which took place earlier this week at the Santa Clara Conference Center. Exhibitors gave attendees the chance to overlay an animal face on top of their own and make it open its mouth or roll its eyes, play a game of Pong in midair, or wave at cartoon characters that popped out of a tile on the floor. All these additions to reality involved some kind of camera--usually in a tablet or smartphone--and software that would recognize the object and trigger the special content.

At the same time, the question was raised: What is augmented reality (AR)? During his keynote, Miles Ludwig, VP digital for Sesame Workshop (the Sesame Street people), showed slides from an upcoming project that uses the Xbox and its Kinect camera to place a child into Elmo's World on their televisions. But Ludwig wondered whether placing a real-world object into a virtual environment was really AR, which usually refers to overlaying virtual objects (like games or animated characters) on the real world. Other examples collected under the AR umbrella included photographs that came with a musical accompaniment and posters that would download a catalog of shoes when you pointed your phone at them.

The slippery definition of just what AR is illustrates...