Although there are differences depending on how finely it has been organized, basically in this system the person who succeeds to the position of iemoto (head master of the house/ school) is at the top, those who are pursuing mastery in that school of artistic accomplishment, etc. are gathered together, and a -hierarchy is constructed.
The art or technique is broken down into kata, or model forms, and what supports the hierarchy is the system by which these kata are imparted and received.
More specifically, there are successive levels of study, and working up from the lowest level, which is the nyûmon or beginner's level, the learner who becomes proficient at the particular level of kata that he or she has been taught so far is issued a certificate (called menkyoja or kyojo, meaning license or permit) from the iemoto.
Once the learner reaches a certain level, that person is permitted to teach others.
In the Edo period, when a person received a certificate, that person was required to submit to the iemoto a sworn oath not to impart the content of the teachings to others. In other words, the teachings were to pass only from a licensed teacher to that teacher's student who had a permit from the iemoto to receive those teachings.
The system also works under the principles of either "complete transmission" or "incomplete transmission."
Complete transmission is where those whose who desire to receive instruction in all the kata that have been passed on to the iemoto are permitted this, while incomplete transmission is where one portion of the kata is not passed on to anyone other than the person who is to succeed as the next iemoto.
The incomplete transmission method effectively means that only the selected iemoto-to-be can become iemoto, whereas the complete transmission system effectively means that anyone who has received all the transmissions might, if he wanted to, call himself an iemoto.
This iemoto system, particularly its hereditary form, sometimes is criticized. However, one aspect of the system is that, owing to it the kata of the artistic accomplishments and martial arts of Japan have been passed down through a long period of time without giving way very much and becoming altered.
Gretchen Mittwer: What is chanoyu?Generationen der Urasenke Iemoto
Das kleine Buch von Gretchen Mittwer, Mitarbeiterin in der Urasenke Kyoto ist zweisprachig in Englisch und Japanisch geschrieben. Es soll denjenigen Japanern als Handreichung dienen, die in die Verlegenheit geraten, Ausländern den Teeweg erläutern zu müssen. Ausländer meinen halt, JEDER Japaner kennt die Teezeremonie in Theorie und Praxis.