Somehow this topic seems so common place and yet no where have I been able to find it spelled out clearly and simply. This reminds me of the joke about a helicopter pilot who's lost in the fog near Seattle, asks where he is and then is able to quickly navigate from there. When asked how he did that, he replied that the person in the window held up a sign saying "You're in a helicopter" which is such a typical engineer's response (accurate and truthful but not helpful or useful) so the pilot knew...