Levenshtein distance : The Levenshtein distance is a metric for measuring the amount of difference between two sequences (i.e., the so called edit distance). The Levenshtein distance between two strings is given by the minimum number of operations needed to transform one string into the other, where an operation is an insertion, deletion, or substitution of a single character.

Mouse base gesture recognition: 

1. Each letter is defined by a n ' 8-directions gesture sequence
2. The mouse moves are saved with the same 8-directions sensibility
3. A Levenshtein distance is calculated from each letter to the user moves
4. The algorithm return the best candidate (lowest levenshtein cost)

  http://www.bytearray.org/?p=91