Value,Description,Reference
low,Low confidence.,[RFC7970]
medium,Medium confidence.,[RFC7970]
high,High confidence.,[RFC7970]
numeric,"The element content contains a number that conveys
        the confidence of the data.  The semantics of this number
        is outside the scope of this specification.",[RFC7970]
unknown,The confidence rating value is not known.,[RFC7970]
ext-value,"A value used to indicate that this attribute is
        extended and the actual value is provided using the
        corresponding ext-* attribute.  See Section 5.1.1 of [RFC7970].",[RFC7970]