The diagram below shows the original curriculum as designed by Ed Parker Sr. (above the solid black line), and the restructured curriculum of Associate Master Francisco Vigoroux (below the line). For the self defenses, the original arrangement is split into two parts, with the first 8 self defenses of the original curriculum being in Level 1 and the second 8 self defenses being in Level 2. The freestyle techniques are assigned completely to Level 2 and there are some minor changes in the placement of the sets and forms.
What Ed Parker Sr. created was unique. It is a systematic approach, using techniques grouped by "families" of attack, to allow the student to see possible defense options based upon the initial attack and the subsequent body positioning of the opponent. The self defense techniques are drills that assist the student in developing neural pathways for specific actions so that, after repeated practice, they can be recombined through "grafting" to defend any situation. "Grafting" involves inserting, deleting, prefixing and suffixing actions together to handle a specific pattern of attack.
There are only so many ways that a person can be attacked, and Ed Parker used those methods of attack to create the "Web of Knowledge" which underlies the order of techniques in each belt. The first self defense in Yellow, "Delayed Sword", is for a lapel grab by the right hand, while the first technique in Orange, "Clutching Feathers" is for a hair grab from the front with left hand. "Twirling Wings" in Purple is for a rear two handed shoulder grab, pulling back, while "Begging Hands" in Blue is for a two handed, double wrist grab from the front. While all of these attacks are "Grabs", the position of the opponent, and the useful targets presented by the opponent are different, creating a different scenario.
American Kenpo has rudimentary principles, stated as succinct phrases, to remind the student how defense is structured. The first principle is "Attack what is attacking you". The second principle is "Establish your base". The third principle is "Disrupt your opponent's base. No matter which self defense you analyze, these three principles are invoked. Kenpo techniques are the final moves to checkmate in a chess match. Once you start checking your opponent, you don't stop, but force the opponent's hand, using your moves to force a specific reaction from your opponent. This reaction sets up your next move to ultimately end up in checkmate.
In Kenpo, after blocking the initial foray by the opponent using the first principle, an attack is made to force an autonomic reaction from your opponent, which exposes targets for the next attack. For example, kicking or striking an opponent in the groin causes the opponent to double over, to skip back, to cover the injured area with one hand or both, lose their wind or perform all four actions. It is definitely disruptive, but depending on your opponent's reaction(s), different targets present themselves, and different attacks become possible. Kenpo thoroughly explores these options through its techniques, and ingrains patterns based upon the targets available.
There are other principles as well, but an overview would not do them justice. For more information, an American Kenpo student is advised to read all of the 5 volumes of the "Infinite Insights into Kenpo" by Ed Parker, Sr. In his own words from "Infinite Insights into Kenpo, Mental and Physical Applications", chapter 2, "(The) Importance of Basics":
"Competent training in Kenpo begins and ends with basics. It would be faulty to assume that once we learn the basics, we should go no further. Consequently, basics should be taught from the embryonic stage to the sophisticated stage. Beginning students should first learn to structure basic moves as they structure words. In doing so, care should be taken to arrange the sequence of movements sensibly so that they correctly spell the desired pattern of motion. Each move learned, whether it is used defensively or offensively, should be viewed as an "alphabet of motion" which, when combined with other moves, forms "words and sentences of motion" that make sense. Pushing the analogy a bit further we can say that whether we are striving to understand the structure of a sentence, or that of a self-defense technique, we must first acquaint ourselves with the rules and formulas that insure their effectiveness."