Comment by bluGill

> Say you have a Car, Engine and Dashboard object.

Then you should burn the whole thing down and start over!

I work on tractors not, cars, but I'm sure the abstractions are similar. Our engine objects are things like [service]AutomationEngine. Our dashboards objects are for a collection of things on secondary displays - meanwhile the thing you would point with your finger as the actual dashboard doesn't have or need a dashboard object. There is an object for things like RPM gauge, or check engine light - this later is a generic fault indicator with a icon field; it is connected to a different messages; and placed in different positions depending on the fault.

The point of the above isn't how tractors are designed, it is how the objects you need to design a real OO system rarely have anything to do with that looks like objects. Nobody ever writes dog and cat objects derived from animal; nobody ever writes triangle objects derived from shape.