If we agree that Kata application should be effective then there are certain rules or principles we can agree on for kata bunkai. My #2 rule for bunkai is that we need to "break the form". We often see kata bunkai where the kata is being applied "as is" without consideration for the nature of natural movements. Shotokan Kata are typically done with an erect posture, long stances and unnatural footwork. We can't fight like this. We need to break the form to apply the kata. Funakoshi 18th precept in his niju kun reads, "Apply kata exactly. Actual combat is another matter. Nakasone writes," It will not do to be shackled by the rituals of kata. Instead, move freely according to the strengths and weaknesses of your opponent." Kata cannot teach us HOW to move when protecting ourselves. It is the principles found in kata that are important.