    # 1999/4/30

    #=============#
    # nonexistent #
    #=============#

    # "nonexistent" is not part of the tabula_rasa hierarchy,
    # but it is useful for recording various forms of nonexistents,
    # such as imaginary concepts, invalid concepts, and
    # anti-concepts.

    # The standard Knowledge Explorer output file lists nonexistent,
    # followed by the existent hierarchy.

Example: sea serpents