1. A method for detecting functional discrepancies between two sequences of firewall rules, said method comprising: receiving a first and second sequences of firewall rules within a computer system; converting said first sequence of firewall rules to a first firewall decision diagram (FDD); converting said second sequence of firewall rules to a second FDD; transforming said first and second FDDs to first and second transformed FDDs, respectively, wherein said first and second transformed FDDs are semi-isomorphic; and comparing said first and second transformed FDDs to determine at least one functional discrepancy between said first and second sequences of firewall rules.