TUIs and Auto-ID Technologies

Literally every physical object may be used as an interface for computerized actions. One may decide to use common (existing) objects as in [15] or may create new ones such as the tokens of [19,3,17]. As both approach aim to integrate the physical objects to the human-computer interface, a mechanism enabling the computer to be aware of the object's presence is mandatory. That is, one must be capable of assigning a unique computer-readable number (or string) to the object. Alternatively, one may transform the object into an electronic device which can be connected to the computer. While the latter solution offers interesting possibilities it requires strong electronic engineering skills and introduces some unwanted constraints. On the opposite, the former method enables very interesting combinations without much efforts (in terms of electronics engineering).
As a consequence, the tiles of [17] and the blocks of [19] or [3] are physical tokens embedding unique identifiers.
There exist various types of support for such identifiers. These are often referred to as Auto-IDs which groups the technologies helping computers to identify objects, animals or people [9]. As an example [19] use iButtons⁴ whereas [3] uses ``silicon serial number''. Eventually [17] use RFID tags on their tiles. It is worth noting that this latter approach is also the most flexible as it enables contact-less identification of the tokens and thus reduces the reliability problems mentioned in [3] (see 4).