Good answer, Kensai, I'll try to add a little bit. There aren't kata in aikido nor jui-jitsu like there are in karate or other punching arts. The exercises that are done are to train the body in the movements that will be used to execute the techniques. Aikido is taught by demonstration and repetition. A technique is demonstrted and then the class pairs off and practices the technique to the satisfaction of the instructor. A technique consists of a particular attack and a particular response. Testing and advancement is by demonstration of progressively complex techniques. At each belt or rank level, the instructor calls out a technique and the person testing has to demonstrate prowess. As the student continues to pass belt exams, there are more and more techniques which are more and more complex. One thought about the objective of testing is to reach a point such that the attack doesn't matter and the number of attackers doesn't matter. The term for this is randori, literally chaotic attack. For upper ranks, 1st kyu and and the dan ranks, randori is a significant part of the exam. From three to six attackers will attempt to subdue the student. The attacks are random, from various punches to grabs - kicks get a little too dangerousthough are not out of the question, and the student must take control of the situation and toss folks aside. Done well, it looks, well, it looks orchestrated, almost too good to be true. But as an attacker and as a defender in those instances, I can tell you is like being in a blank space. You don't hear anything except your own breathing. When it works, it's like magic. And when it doens't, and I've have trainging sessions that haven't, it's like being in a car wreck. Aikido can't really be studied by a single person. It takes two or more to really study it. There aren't individual exercises except for the movement. And that won't teach you technique.
