Martin Fowler

"Modeling Principle: Models are not right or wrong; they are more or less useful."

"When you feel the need to write a comment, first try to refactor the code so that any comment becomes superfluous."

"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, its 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."

"The key is to test the areas that you are most worried about going wrong. That way you get the most benefit for your testing effort. It is better to write and run incomplete tests than not to run complete tests"

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

"Comprehensiveness is the enemy of comprehensibility"

"The definition I use for a pattern is an idea that has been useful in one practical context and will probably be useful in others"

"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"

"It is commonly said that a pattern, however it is written, has four essential parts: a statement of the context where the pattern is useful, the problem that the pattern addresses, the forces that play in forming a solution, and the solution that resolves those forces. … it supports the definition of a pattern as "a solution to a problem in a context", a definition that [unfortunately] fixes the bounds of the pattern to a single problem-solution pair"

"Transparency is valuable, but while many things can be made transparent in distributed objects, performance isnt usually one of them."

"One of the things Ive been trying to do is look for simpler or rules underpinning good or bad design. I think one of the most valuable rules is to avoid duplication. "Once and only once" is the Extreme Programming phrase."

"Often youll see the same three or four data items together in lots of places: fields in a couple of classes, parameters in many method signatures. Bunches of data that hang around together really ought to be made into their own objects."