preassumptions of the situation to use a closed single valued transformation model

Sorry if my question is completely wrong at this list.

I am new on this list and I thought it is about cybernetics and control of
systems.

My question for this list is the following:

I am looking for a publication where it is made clear which assumptions of
the situation must be made that it is worth or even right to use a
transformation model for this situation which is single valued and closed?

I hope my question is right at this list - if not I am very sorry.

Best regards

Roland