1. A machine readable medium containing executable program instructions which cause, when executed, a data processing system to perform a method comprising: generating artificial entities in response to a source character string, at least two of the generated artificial entities corresponding to separate substrings of the source character string, the separate substrings sharing at least one common character of the source character string; converting at least a first portion of the source character string to a second character string through a first data structure containing the generated artificial entities including the converted second character string; and converting at least a second portion of the source character string to a third character string through a second data structure containing predetermined regular entities; providing an output based upon the second character string and the third character string.