Aikido's immediate appearance is somewhat magical. This traditional Japanese Martial Art uses various joint locks and throws, but is not effective self defence because it takes years to master. It's respected as an art form, but should not be used or taught for self defence or combat. The theory to use the attackers strength and aggression against them is dangerously wrong and gives practitioners a fated confidence. Any Aikido you see in a video is most likely to be a carefully choreographed dance with the practioners who have trained in it for years. It relies far to much on having a willing opponent in training. Even the Aikido method to a basic forward roll is faulted by using poor body mechanics. I do like the techniques because they are very cool looking, and it's a beautiful flowing traditional system. But it pretty much assumes that every attack is a wrist or lapel grab. There is no knife, blunt weapon or firearms training.
Relationship to Krav Maga
Aikido has little or nothing in common with a reality based self defence system like Krav Maga.