1. A method for normalizing input strings, the method comprising the steps of: (a) receiving the input strings; (b) linguistically analyzing the input strings to generate a first representation of each of the input strings; each of the first representations including linguistic information; (c) skeletising each of the first representations to generate a corresponding second representation for each of the input strings; said skeletising step replacing the linguistic information with abstract variables in each of the second representations; and (d) storing the second representation as normalized representations of the input strings.