  People learn whenever and wherever possible, and whatever they like or
encounter--Mathematics, Drama, Art, Languages, Physics, Philosophy, and so on.
With the bursting of knowledge, evaluation of one's possession of knowledge
becomes increasingly difficult. There are a lot of demands to evaluate one's
understanding of a piece of knowledge. Assessment of understanding of knowledge
is conventionally through tests or interviews, but they have some limitations
such as low-efficiency and not-comprehensive. This paper proposes a method
called Understanding Tree to estimate one's understanding of knowledge, by
keeping track of his/her learning activities. It overcomes some limitations of
traditional methods, hence complements traditional methods.
