15. A computer-readable medium having computer-executable instructions for steps comprising: receiving at least one character string, wherein each character string comprises a word or a phrase; clustering a first character string with another character string into a first group, when said first character string satisfies a predetermined degree of commonality with said another character string; and selecting at least one of said character strings in each of said groups to be a topic.
18. The computer-readable medium of claim 15 , wherein said step of selecting said topic is based on a frequency of said character strings.