Edit a UnitA Unit contains static Knowledge, and may contain one or more Rule. In this example, Knowledge field includes two sentence as following :
#botname[PERSON] is a chatbot.
#botname's name is #botname[SIGN].
#botname is a special keyword defined by the system. It is used for replacement the name of the Chatbot. The purpose of the definition of this keyword is there is no need to replace the chatbot’s name one by one when the unit is shared by the others. Provided the name of the Chatbot is Robert.
These two sentences are equal to
Robert[PERSON] is a chatbot.
Robert's name is Robert[SIGN].
Two Roberts tagged as  represent person, and Robert tagged as  represents a name and it is different from the formers, so we use [SIGN] to mark it.