Here is a good overview of existing approaches to approximate sequence matching - http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.96.7225&rep=rep1&type

Here is a good overview of existing approaches to approximate sequence matching - http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.96.7225&rep=rep1&type=pdf http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.96.... . I also wrote in a fair bit of detail about solving the similar problem of searching through LaTeX syntax trees - http://scattered-thoughts.net/one/1291/799313/731344 http://scattered-thoughts.net/one/1291/799313/731344 . Adapting my code to searching by Hamming distance should be trivial should anyone want to play around with image searches.