Transparency is valuable, but while many things can be made transparent in distributed objects, performance isn't usually one of them. - Martin Fowler

The second problem [with using UML for the purposes of this book] is that the Unified Modeling Language concentrates on implementation modeling rather than conceptual modeling

Often designers do complicated things that improve the capacity on a particular hardware platform when it might actually be cheaper to buy more hardware.

Refactoring is a disciplined technique for restructuring an existing body of code, altering its internal structure without changing its external behavior. Its heart is a series of small behavior preserving transformations. Each transformation (called a 'refactoring') does little, but a sequence of transformations can produce a significant restructuring. Since each refactoring is small, it's less likely to go wrong. The system is also kept fully working after each small refactoring, reducing the chances that a system can get seriously broken during the restructuring.