1. A method performed by system of one or more data processing devices, the method comprising: receiving, at the system, information characterizing a first user interaction with a touchscreen; receiving, at the system, information characterizing a second user interaction with the touchscreen; the system assigning a probability to each of two or more interpretations of a combination of the first user interaction and the second user interaction, each of the interpretations construing the combination as a different pair of characters, each of the probabilities embodying a likelihood that the first user interaction and the second user interaction represent the respective pair of characters, wherein the system assigning the probability to each of the two or more interpretations of the combination of the first user interaction and the second user interaction includes: assigning first probabilities to interpretations of the first user interaction, independently assigning second probabilities to interpretations of the second user interaction, and determining the probabilities assigned to the interpretations of the combination using the first probabilities and the second probabilities; the system using the two or more interpretations to search a collection of data for objects that are each identifiable by one of the two or more interpretations; and the system outputting identifiers of at least some of the objects.