A Scale represents the [VIM] concept of a "measurement scale" that is defined as an "ordered set of quantity values of quantities of a given kind of quantity used in ranking, according to magnitude, quantities of that kind." A Scale specifies one or more fixed values that have a specific significance in the definition of the associating QuantityKind. For example the "thermodynamic temperature" kind of quantity is defined by specifying the values of 0 and 273.16 kelvin as the temperatures of absolute zero and the triple point of water respectively. A Scale does not always need to specify a unit. For example the "Rockwell C Hardness Scale" or the "Beaufort Wind Force Scale" are ordinal scales that do not have a particular associated unit. Similarly, subjective scales for a "priority" or "risk" kind of quantity with e.g. value definitions 0 for "low", 1 for "medium" and 3 for "high" do not have a particular associated unit.