Often times in the sport of Judo a failed throw or sweep ends with your opponent turtled up on the ground with his/her arms and legs in, and paying attention to coach Wu Tang by protecting their necks. In Brazilian Jiu Jitsu we have a number of techniques and strategies where we attack the back, but in Judo the strategy is a bit different. A held and controlled pin for instance means you win (submission not necessary), and this likens to the Samurai roots of Judo where on the battlefield one would throw, pin, and once control is established you would draw your weapon and finish the opponent. A pinned opponent on their back is both exposed and unable to defend against a furnished weapon.
So it only makes sense that Judo has developed a number of methods to turn your opponent over to attack and/or pin them, and all too often these subtle attacks are overlooked in Judo and all but unknown in BJJ! Here is a clip of 7 solid competition level turnovers.