To give you an idea of our knife defence (as I teach it), it begins with awareness drills, taking notice of whether you can see both hands of an approaching threat, watching when hands "disappear" to produce weapons (or potentially, at least), methods of maintaining distance if unsure, ways of checking if they have a weapon (verbal challenges, for want of a better term, essentially removing their sense of the element of surprise), all with the aim of not engaging in the first place. From there we deal with the appearance of a knife (or any other weapon), with a verbal recognition of the weapon (which ensures that you recognize it yourself, as well as ensuring that any witnesses see what's happening, and demonstrating to the attacker that there is no surprise anymore). Then, we deal with technical methods for handling an attack, starting with simple drills to ensure protective actions (jamming and blocking methods combined with movement "inside" the arc of the attacking weapon, moving on to controlling methods, then onto disengaging and disposal methods), then moving onto actual "techniques" against the attack. These all follow the same essential pattern, which is to commit completely to the action decided upon, whether an evasive leap out of the way, or moving in to control and counter; when moving in to ensure complete control over the knife arm immediately, taking into account the natural response of the attacker (which is to try to retrieve their weapon), before moving onto a disposal/control/counter.
As you can see, a safe escape is the dominant aim as soon as possible, but the training needs to take into account everything from seeing the threat early and escaping, to handling an attacking opponent, otherwise you're missing a large section of necessary skills. But when it comes to the disarms/techniques used, they need to be realistic, which means that you need to have a realistic understanding of knife assaults and defence. Within our traditions there are plenty of knife/short blade defences, most notably within Gyokko Ryu, Koto Ryu, and Takagi Yoshin Ryu (if you know where to look there....). Now, those techniques are great, however if taken just as they are, they don't work against modern knife assaults. The principles and tactics found in them, though, do. But the important thing is that our modern knife defences are trained against realistic (modern) attacks, with realistic responces from the attackers. Ideally, when done properly, the students won't have an inflated sense of security against a knife.... after training knife defence with my guys for a couple of months, I asked for some feedback on the way we were approaching it. The comments I got back were that the students hadn't realized just how scary, and dangerous, knife defence is. And that comes down to going up against realistic attacks.