What my limited understanding of aikido weapons styles leads me to beleive is: Weapons in Aikido help the open hand tecnique. This is not to say that they are not martial in application as well, but they do help with unarmed style. We also practice weapons takeaways. We train against short staff (jo), sword (bokken witch is a wooded practice katana), and knife (tanto). I really enjoy the open hand vs. weapons training. I perfer to train against the tanto as this seems more likely of a situation as opposed to a sword.