Ed Parkers commercial vehicle for spreading kenpo was based on a thorough understanding of the "laws of motion." He created a vocabulary of motion...terms and ideas that explored and expressed martial movement in simple enough terms, that it could ideally be taught, understood, shared, and discussed by folks on opposite sides of a continent, and everybody be on the same page.
Mr. Parker took an engineers mind to classifying the types of motion the body was capable of and assigning them to categories. These categories then were used to elucidate basics. Basics combined to form self-defense techniques, sets, and forms, each presumably illustrating several of the laws of motion he delineated in his writings and standardized system.
Trouble was, it didn't quite pan out as planned. Mr. Prker rarely ever did techniques the same way twice, choosing to use them as vehicles of communication to illustrate concepts, principles, or ideas under discussion. But the people in the room would say, "This is how Mr. Parker taught it to me", and canonize it as "the right way". The motion model he proposed allowed for -- and even encouraged -- rearrangement: The idea that there really was no right or wrong way; techniques are merely arrangements of basic movements, toward a contextual objective. As the context changes, we must change with it...which means, don't try to do 5 swords against a punch. Maybe use the block and chop, but since another punch is coming, but something else is going to be happening by the time you get this far, be ready to adapt by changing up your approach to the liquid situation.
So, people out there getting fixations on right/wrong way to approach a model that was left open and permissive for recruiting sakes (on the dark side), and flexibility to adapt (on the bright side). But (and this is where people get uppity), Mr. Parker -- when he would do his own kenpo -- would move in certain ways and use his body in certain ways that he never specifically taught as part of the cirriculum, or relayed as a requirement. He would use little "isms" to ramp up his own effectiveness, but not hold seminars on those isms...rather, just do them while teaching a session on some more abstract concepts. If you caught the isms, good for you. If not, whatever.
SL4 is Docs effort at categorizing those isms, and placing them into the system cirriculum as requirements. Rather than just waving your arms around and saying you're doing some technique X, HOW, WHY, and WHEN you move your body in the course of executing that technique is just as important as the tech itself. Rearrangement theory is avoided until people have learned the basics properly...a great response to a problem inherent in AK, which is...too much material, too soon, causes students to stop training basics at one level to rush on to the next = lousy or ineffectual basics. Kinduva, "You don;t know what you don;t know, so stop trying to second guess what's possible, and just pay attention to getting your basics right...we'll look at the other stuff when the time is right.
Techniques are used to teach and engrain mechanically correct martial movement, rather than as mini-episodes of fight scenes. Once mechanics are owned, application follows more logically form the sounder foundation.
If someone wanted a simpler synopsis, I offer: AK focuses more on high-speed, blunt force trauma to vital targets; SL4 focuses more on tactical strikes to nerves and other structurally supportive tissues. AK focuses on speed first, hoping structure follows (not all, but enough to be an issue). SL4 focuses on proper movement, allowing speed and power to develop naturally as a side effect of proper techique.
To these ends, basics are challenged to ensure proper mechanical alignment in the direction of resistance to impact. Skills in delivery are emphasized instead of just blasting a guy. Appropriate response to force escalation is emphasized...Doc's an LEO, and so are most of his students. A search on Kenpotalk will also yield some writings about points of emphasis in SL4. Worth the read.
Hope it helps,
Dave...not quite motion kenpo, but not enough SL4 either. But working on it.