In drawing up an E-A-R diagram for a program (doing object-oriented design, if you must be seen at a table at Maxim's), you're led inexorably toward a study of the problem and its context and away from the solution and its technology. This--and not multiply inherited, polymorphic, virtual mix-in friends--is the key insight of object-oriented methodology: Use E-A-R diagrams to do program design. After all, the understanding of and insight into the problem is the wellspring of program simplicity and implementation efficiency. A good architect studies bricks once, but studies people every time he designs a new building.