A tangible user interface (TUI) is a user interface in which a person interacts with digital information through the physical environment. The initial name was Graspable User Interface, which is no longer used. The purpose of TUI development is to empower collaboration, learning, and design by giving physical forms to digital information, thus taking advantage of the human ability to grasp and manipulate physical objects and materials. This was first conceived by Radia Perlman as a new programming language that would teach much younger children similar to Logo, but using special "keyboards" and input devices. Another pioneer in tangible user interfaces is Hiroshi Ishii, a professor at the MIT who heads the Tangible Media Group at the MIT Media Lab. His particular vision for tangible UIs, called Tangible Bits, is to give physical form to digital information, making bits directly manipulable and perceptible. Tangible bits pursues the seamless coupling between physical objects and virtual data.
Characteristics There are several frameworks describing the key characteristics of tangible user interfaces. Brygg Ullmer and Hiroshi Ishii describe six characteristics concerning representation and control:
Physical representations are computationally coupled to underlying digital information. Physical representations embody mechanisms for interactive control. Physical representations are perceptually coupled to actively mediated digital representations. Physical state of tangibles embodies key aspects of the digital state of a system Ullmer, Ishii, and Robert J. K. Jacob further developed a token+constraint framework, in which discrete physical objects (tokens) represent digital information and are manipulated within confining regions (constraints) that map to digital operations. Eva Hornecker and Jacob Buur describe a structured framework with four themes:
Tangible manipulation: material representations with distinct tactile qualities, which are typically physically manipulated. A typical example is haptic direct manipulation: can user grab, feel and move important elements in the interface? Spatial interaction: tangible interaction is embedded in real space; interaction occurs as movement in this space. An example is full body interaction: can the user make use of their whole body? Embodied facilitation: the configuration of material objects and space affects how multiple users interact jointly with the tangible user interface. Examples include multiple access points: can all users in the space see what is going on and interact with central elements of the interface? Expressive representation: expressiveness and legibility of material and digital representations employed by tangible interaction systems. An example is representational significance: do physical and digital representations have the same strength and salience? According to Mi Jeong Kim and Mary Lou Maher, the five basic defining properties of tangible user interfaces are as follows:
Space-multiplex both input and output. Concurrent access and manipulation of interface components. Strong specific devices. Spatially aware computational devices. Spatial re-configurability of devices.
Comparison with graphical user interfaces A tangible user interface must be differentiated from a graphical user interface (GUI). A GUI exists only in the digital world, whereas a TUI connects the digital with the physical world. For example, a screen displays the digital information, whereas a mouse allows us to directly interact with this digital information. A tangible user interface represents the input directly in the physical world, and makes the digital information directly graspable. A tangible user interface is usually built for one specific target group, because of the low range of possible application areas. Therefore, the design of the interface must be developed together with the target group to ensure a good user experience. In comparison with a TUI, a GUI has a wide range of usages in one interface. Because of that it targets a large group of possible users. One advantage of the TUI is the user experience, because it occurs a physical interaction between the user and the interface itself (E.g.: SandScape: Building your own landscape with sand). Another advantage is usability, because the user knows intuitively how to use the interface by knowing the function of the physical object. So, the user does not need to learn the functionality. That is why the Tangible User interface is often used to make technology more accessible for elderly people.
Examples A simple example of tangible UI is the computer mouse: Dragging the mouse over a flat surface moves a pointer on the screen accordingly. There is a very clear relationship about the behaviors shown by a system with the movements of a mouse. Other examples include:
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