Tangible User Interfaces - Clever or Cumbersome

Tangible User Interfaces (TUI) are a very old idea made new by connecting physical objects to digital data.

I think of this connection as "baubles to bits".

In a TUI real world physical objects assume digital personalities. Such objects instantiate a rather schizophrenic, hybrid existence.

These objects may be called Tokens or 'tangibles' (Ishii).

They carry all the characteristics of physical objects such as weight, inertia, three dimensionality, color, shape, and so on. They also carry certain human created expectations of behavior, such as permanence, location inertia, ambient temperature, to name only a few. All Tokens inherit these characteristics and expectations simply because they are physical objects. Tokens add to these characteristics and expectations novel properties based upon often arbitrary digital paring.

Digital paring is the association of some meaning or value existing within a digital representation with a physical object or a physical object's characteristic. Here digital representation can be any system of digital variables which exist in a simulation, data base, model, or abstraction.

Consider a digital representation to be an abstraction of the environmental characteristics of a bedroom. Temperature, humidity, and light levels would be specific environmental characteristics. each of these characteristics is represented by a variable: T, H, L. These variables have numeric values and limited range. In a TUI these variables would be paired with physical objects or an object's characteristics.

One can conceive of a physical object, a Token, who's color would represent temperature, who's brightness would represent light levels, and who's ...

Here we begin to see the limitations of using a physical object to represent digital data. Perhaps the Tokens surface wetness should represent humidity. Or perhaps the Token's height.

If we wish to use our TUI to control the bedroom's environment then we must be able to manipulate the Token along each of the three dimensions. Certainly we can construct a physical object who's color is related to it's x/y plane rotation. So, Token rotation can easily be associated with temperature.

But now we have two characteristics of our physical object representing temperature. Perhaps we should have chosen Token rotation as our temperature indicator. But then we must create a Token which can rotate itself.

Since our TUI is controlling a real world physical system (environment), command input is not going to immediately match measured value. Unlike pure digital systems, the temperature of a room has considerable inertia. Heaters must come up to temperature. Air must be passed through the heater. Objects in the room must heat up, The temperature sensor must change temperature.

Thus we find that in the control of real word systems our TUI must represent not only existing values but also desired values. This complicates the already difficult task of pairing digital and physical characteristics.

TUIs are seductive. They are potentially powerful. And yet they must be cleverly designed less they become merely a cumbersome old idea made new by a digital patina.