Object Oriented Design: ideas
	• Always assume that an object has no insight into the internal structure of another object • Play close attention to this! • All activities on objects other than itself must be achieved by performing an operation, not by direct manipulation of the internal data • Always ask yourself “how can an object of this class carry out an operation on another class’ data? • This is a hard question – especially since you may not be aware at the design phase of all of the implementation details