What is the difference between "Design Function" and "Objective Function"?

Question

What is the difference between "Design Function" and "Objective Function" in the study of Optimization?

Answer 1

In the link you provided, design functions are the objective function and constraints for the optimization problem. Objective function is just the design function being minimized (or maximized).

I am not used to seeing such terminology, but this appears to be what is intended in the link.