Speaking of which, it is my understanding that a menkyo kaiden is a certificate saying you've learned all the art can teach and now you are responsible for the improvement and progression of the art. I don't think it automatically makes you the Soke but I believe there is only one available in an art. I'm pretty sure it indicates tenth dan but tenth dan doesn't necessarily grant you a menkyo kaiden or sokeship. In fact I don't believe in sokeship. There's only one soke for an art, he founded it. When he dies, his heir (son or otherwise) may inherit the system but he is only refferred to as soke as a formality. If he is worthy, however, the heir is the one who is granted the menkyo kaiden and is the new headmaster. I think. Lineage is pretty linear and therefore traceable.