{
  # double not boolean expression
  # empty configs are not accepted by Kea
  "Dhcp4": {
    "valid-lifetime": 1800,
    "client-classes": [
      # use double not in a reductible match if
      {
        "name": "reductible",
        /// from: match if not not ((option dhcp.host-name) = 'www.example.com') or ((option dhcp.host-name) = 'www.example.org')
        "test": "(option[12].hex == 'www.example.com') or (option[12].hex == 'www.example.org')"
      },
      # use not with !=
      {
        "name": "other",
        /// from: match if not (option dhcp.host-name) != 'www.example.com'
        "test": "option[12].hex == 'www.example.com'"
      }
    ]
  }
}