Agendas are all about continuity and patterns. The characteristic circles in the Agendas would represent specific steps and decisions made in life or, if preferred, during a single day. Lines represent the order. They symbolize the patterns we continuously create moving through life, by thinking, making decisions, or even remembering. This way becoming a kind of portrait of ourselves or the chosen period of time.
However the meaning is too universal to be closed by such an interpretation. The tree of continuity concerns every possible area in space – all kind of mappings, or simple board games.