Lambda the Ultimate

In my reading so far on ML type inference algorithms, the object seems to be to infer the most general type of expressions. If I have the terminology correct this is the "principal type".

Can someone point me at algorithms for inferring the most-specific or least-general types in ML programs? I'm interested in analysis methods, type inference being one of them, for find information about a program. So rather than most general types to encourage reuse of code, I'd like to find the most-specific types to see exactly and only the way the functions are being used in a program.

thanks in advance!
bill