I was reading this free book online book about SmallTalk and as I was reading pages 34-41, I was thinking, "dammit, I wish I would have seen this back in college." Those pages show what is probably one of the best examples of composing/decomposing an OOP system that I've seen to date.
Also, the following is probably one of the best quotes I've ever read with respect to the same subject. Again, it reminded me of when I was in college after learning how to program with C and then afterwards moving on to my Object Oriented Programming with C++ course the next semester:
The aim in object oriented programming is to shift the focus of attention from procedures that do things to data round to data which is asked to do things. The task is not to define the procedures which will manipulate data but to define data objects, their attributes and the way in which they may be examined or changed. Data objects (and procedures) can communicate with data objects only through narrow, well defined channels.
