MATH.2:5.4 - Normalize labelled values before identifying them

A temperature-checking method accepts values labelled Celsius or kelvin. It converts them to kelvin, then tests membership in the inclusive interval [273.15,303.15]. Grouping inputs by their numeral alone loses the answer: 20 Celsius becomes 293.15 kelvin and passes, while 20 kelvin fails.

Let n(v,C)=v+273.15 and n(v,K)=v. Identify inputs when their n-values agree. Every input has a normalization result, and identified inputs have equal results; both the normalization and the following interval test therefore descend to these classes. This uses the separate input and output sorts of :4.1.

A later question about the original unit cannot be answered from the class alone. Retain the label when that question matters. If the description of the working method places comparison before normalization, Method Engineering ME.12:4.4 helps locate and repair that contradiction. The mathematical compatibility test and the repair of the described work answer different parts of this example.