Law Of Demeter
Excellent concept and this is an excellent article on it: http://www.javaguy.org/papers/demeter.pdf. The examples are in Java which makes my life easier at the moment. But, you would be amazed how ground breaking this concept is to a lot of folks. It's common sense to me and other object hard-core folks, but it is quite new to A LOT OF JAVA folks. Anyway, excellent article and explains the principle in a simple straightforward manner. All technical articles should be like this: Well-written, easy to digest, offers one concept, and keeps it simple.