Token and Constraints framework
The Tangible Query Interface is a great demonstration of the Token and Constraints paradigm. The query wheels and bars are tokens that users can manipulate to alter their queries to the database, and the limitations to the ways that users can interact with them are the constraints. These constraints help simplify and streamline interaction with the TUI, as they reduce the number of options the user has in choosing how to manipulate the tokens.
The query wheels and bars of TQI represent the parameters of a database query. It is this association with data that makes them Tokens. Direct manipulation of the wheels or bars results in changes in the parameters of the query statement. TQI doesn’t exactly map pieces of data to objects on a 1 to 1 basis– rather it is the abstract idea of parameters for the data to be separated by that is being represented by the Tokens.
The boundaries in which the query wheels and bars can be placed and moved represent the way the user may manipulate the parameters of their query. The query rack is one type of constraint in TQI; circle-shaped indentationed in the query rack serve as a very straight-forward indication to the user that the query wheel is meant to be placed there, since the shapes match and the pieces fit. Similarly, the query bars are sized so that they fit into the horizontal board of the query rack, so it is apparent to the user that they belong there.
Once a query wheel has been loaded into its proper place in the query rack, the user has very few options as to how they may now interact with the query wheel. They can either remove the wheel and replace it with another, or they can move the query wheel within the confines of the circle indentation. Those movements are limited to turning the wheel like a nob– this limitation is imposed by the shape of the constraint, and are a method of pointing the user in the right direction by giving them only a few ways to manipulate the token. This is effective because the query wheel is intended to be turned up and down by the user, an action that translates to the computer that the user wishes to change the range of the parameter that the query wheel corresponds to.
The user’s interactions with the query bar are also limited by the constraint of the query rack. The shape of the query rack not only indicates that the user should place the bar in it, but the extra space in the query rack encourages the user to slide the bar across the query rack horizontally. This leads into a certain mechanism of the query bar, which is the fact that bars that are placed close together represent the intersection of those two parameters, while bars with space between them represent the union of those two parameters.
Tangible Interaction framework
The user operates TQI by physically interacting with query wheels and bars, which are objects that can be moved and placed within the boundaries of TQI. Those interactions translate into manipulation of the data via the change of parameters in the query or change in range of the parameters. Thus, the user feels as though they are directly manipulating the data by interacting with these physical objects.
One way TQI utilizes spatial interaction is in how the query bars can be moved within the query rack. The user can either place the query bars adjacent to each other or with space between them, and the bars’ proximity will dictate how the parameters interact. If they are next to each other, the query will return the AND of the two parameters, and if they are apart, the OR of the parameters will be returned. The intuition that things that are closer together share a stronger relationship than things that are apart makes this an easy mechanism for the user to understand.
The shape and size of the query rack constrain the behavior of the user by encouraging them to only pursue the few interactions available to them. The LCD display that outputs the results of the query is an access point for the user that allows them to see how their manipulations of the query wheels and bars is effecting the results from the database, and thereby realize what type of action will get them to the result they want to see.
The feedback provided by the LCD screen that displays the results of the query is what binds the user’s interactions with the physical tokens to the manipulation of the digital information in the database. Since the LCD screen changes in real time corresponding to how the user moves the query wheels/bars, there is a clear link between the user’s actions and the manipulation of data. The scatterplot that shows the results on a graph with the range of the parameters facilitates this link, as the query wheels/bars represent those parameters.