Martin Fowler

British programmer

Martin Fowler (born 1963) is a British software engineer, author and international speaker on software development, specializing in object-oriented analysis and design, UML, patterns, and agile software development methodologies, including extreme programming.

Any fool can write code that a computer can understand. Good programmers write code that humans can understand.
Martin Fowler, 2008.


  • People also underestimate the time they spend debugging. They underestimate how much time they can spend chasing a long bug. With testing, I know straight away when I added a bug. That lets me fix the bug immediately before it can crawl off and hide. There are few things more frustrating or time-wasting than debugging. Wouldn't it be a hell of a lot quicker if we just didn't create the bugs in the first place?
    • Martin Fowler (2002) as cited in Evolutionary Design: A Conversation with Martin Fowler, Part III by Bill Venners, November 18, 2002.
  • Transparency is valuable, but while many things can be made transparent in distributed objects, performance isn't usually one of them.
    • Fowler (2003) in: Software development. Vol. 11. p. 99
  • 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.
    • Martin Fowler at as cited in: Lawrence Bernstein, C. M. Yuhas (2005) Trustworthy Systems Through Quantitative Software Engineering. p. 266
  • One of the things I've 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.
    • Martin Fowler as cited in: James Shore, Shane Warden (2007) The Art of Agile Development. p. 319
  • Often designers do complicated things that improve the capacity on a particular hardware platform when it might actually be cheaper to buy more hardware.
    • Martin Fowler (2012) Patterns of Enterprise Application Architecture

Analysis Patterns: Reusable Object Models, 1997Edit

  • Modeling Principle: Models are not right or wrong; they are more or less useful.
    • p. 2
Unified Modeling Language (UML) concentrates on implementation modeling rather than conceptual modeling
Martin Fowler, 1997
  • 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
    • p. 6
  • 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
    • p. 8

Refactoring: Improving the Design of Existing Code, 1999Edit

Martin Fowler, Kent Beck, John Brant, William Opdyke, and Don Roberts (1999) Refactoring: Improving the Design of Existing Code. Addison-Wesley.

  • When you find you have to add a feature to a program, and the program's code is not structured in a convenient way to add the feature, first refactor the program to make it easy to add the feature, then add the feature.
    • p. 7
  • Any fool can write code that a computer can understand. Good programmers write code that humans can understand.
    • p. 15
  • Refactoring (noun): a change made to the internal structure of software to make it easier to understand and cheaper to modify without changing the observable behavior of the software.
    To refactor (verb): to restructure software by applying a series of refactorings without changing the observable behavior of the software.
    • p. 33-43 as cited in Militiadis Lytras, Patricia Ordóñez de Pablos, Ernesto Damiani (2011) Semantic Web Personalization and Context Awareness. p. 111
  • Often you'll 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.
    • p. 81
  • When you feel the need to write a comment, first try to refactor the code so that any comment becomes superfluous.
    • p. 88
  • 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
    • p. 98.

A Brief Guide to the Standard Object Modeling Language, 2004Edit

  • Steve Mellor and I independently came up with a characterization of the three modes in which people use the UML: sketch, blueprint, and programming language. By far the most common of the three, at least to my biased eye, is UML as a sketch. In this usage, developers use the UML to help communicate some aspects of a system. As with blueprints, you can use sketches in a forward-engineering or reverse-engineering direction. Forward engineering draws a UML diagram before you write code, while reverse engineering builds a UML diagram from the existing code in order to help understand it.
    • p. 2

UML Distilled: A Brief Guide to the Standard Object Modeling, 2004Edit

Martin Fowler (2004) UML distilled: a brief guide to the standard object modeling language.

  • Graphical design notations have been with us for a while... their primary value is in communication and understanding. A good diagram can often help communicate ideas about design, particularly when you want to avoid a lot of details. Diagrams can also help you understand either a software system or a business process. As part of a team trying to figure out something, diagrams both help to understand and communicate that understanding throughout a team. Although they aren't, at least yet, a replacement for textual programming languages, they are a helpful assistant... Of these graphical notations, the UML's importance comes from its wide use and standardization within the OO development community.
    • p. xxvi
  • Comprehensiveness is the enemy of comprehensibility
    • p. 32

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