When should fv! domain prefix be used?

The fv! domain prefix should be used when calling a function that allows variables to be passed to one or more inputs. This prefix is essential in contexts where you are working within a function that can accept variable arguments, as it ensures that the function correctly identifies and utilizes the function variables that are defined in the specific scope.

Using the fv! prefix allows for more dynamic and flexible expressions, as it refers explicitly to the function variables created in the local scope of that specific function. This is crucial for maintaining clarity and functionality, especially in complex expressions where multiple variables may be in play.

In contrast, referencing fixed variables in expressions typically does not require the fv! prefix, as fixed variables are accessed directly without needing to specify the function context. User interface display configurations focus on layout and visual elements, and process variable values are accessed through a different context altogether, usually within a process model. In all these cases, the use of the fv! prefix is specifically tied to the dynamic nature of function variable inputs.