Re: Uniqueness principle
The uniqueness principle says, that for given geometry and initial conditions, there is one and only one solution to Maxwell's equations.
How does one apply it in practice? Well, one doesn't. At least not directly. It does not help you solve the problem; however, if you can find a solution, you know it's the solution.
It does allow us to do comparisons, e.g., simulation vs. measurements. It also allows us to bicker endlessly about who is better: CST or HFSS. Because both should be converging to the same solution.