I was able to successfully complete the example of the CarLot. I made lots of simple mistakes, but was able to find and fix them all. My question is when would I use an ObjectController instead of ArrayController? If my application needed to have a single Car per document, would I be correct in assuming that I would use an ObjectController instead of an array controller? Of course, I would not use the tableview, just simple bound controls. How would I go about changing the existing carlot application?