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Hi, all: This is the basic implementation of tf-idf scheme (basic scheme used in SMART) that can be used in the Xapian. It might still need some futher revision, but I believe it works anyway.:) I modified the weight.h to define a subclass Tf_idfWeight and add a new file tf_idf.cc in ../weight in the repo, to implement Tf_idfWeight. Here is the git diff patch: https://gist.github.com/2422049