Thanks for the answer
What I am trying to write control system that has what term as collections of controls, In my case there would be collection of bins that would have collection of gates and so on (I am software developer so I am used being able to do this). These collections will be constant at particular site but change at the next implementation. So what I want to know how you would go about this. The problem is that a bin may variable number of gates. I hope this makes senses
Cheers