Derived tag in 7.9.2-RC1

A new type of tag : “derived tag” have appeared in 7.9.2-RC1.
What are their purpose ?

One use is to create sort of a bi-directional expression tag. Imagine an OPC tag with a value that is in celsius, but you want the value displayed in Ignition converted to Fahrenheit for operators, but then need it converted back to celsius upon being written to.

edit: or maybe a better way to think of it is as enabling a “universal scaling”.