Software development is a young profession, and we are still learning the techniques and building the tools to do it effectively. I've been involved in this activity for over three decades and in the last two I've been writing on this website about patterns and practices that make it easier to build useful software. The site began as a place to put my own writing, but I also use it to publish articles by my colleagues.

In 2000, I joined Thoughtworks, where my role is to learn about the techniques that we've learned to deliver software for our clients, and pass these techniques on to the wider software industry. As this site has developed into a respected platform on software development, I've edited and published articles by my colleagues, both ThoughtWorkers and others, to help useful writing reach a wider audience.

photo of Martin Fowler

photo: Christopher Ferguson

Martin Fowler

A website on building software effectively

If there's a theme that runs through my work and writing on this site, it's the interplay between the shift towards agile thinking and the technical patterns and practices that make agile software development practical. While specifics of technology change rapidly in our profession, fundamental practices and patterns are more stable. So writing about these allows me to have articles on this site that are several years old but still as relevant as when they were written.

As software becomes more critical to modern business, software needs to be able to react quickly to changes, allowing new features to be be conceived, developed and put into production rapidly. The techniques of agile software development began in the 1990s and became steadily more popular in the last decade. They focus on a flexible approach to planning, which allows software products to change direction as the users' needs change and as product managers learn more about how to make their users effective. While widely accepted now, agile approaches are not easy, requiring significant skills for a team, but more importantly a culture of open collaboration both within the team and with a team's partners.

This need to respond fluently to changes has an important impact upon the architecture of a software system. The software needs to be built in such a way that it is able to adapt to unexpected changes in features. One of the most important ways to do this is to write clear code, making it easy to understand what the program is supposed to do. This code should be divided into modules which allow developers to understand only the parts of the system they need to make a change. This production code should be supported with automated tests that can detect any errors made when making a change while providing examples of how internal structures are used. Large and complex software efforts may find the microservices architectural style helps teams deploy software with less entangling dependencies.

Creating software that has a good architecture isn't something that can be done first time. Like good prose, it needs regular revisions as programmers learn more about what the product needs to do and how best to design the product to achieve its goals. Refactoring is an essential technique to allow a program to be changed safely. It consists of making small changes that don't alter the observable behavior of the software. By combining lots of small changes, developers can revise the software's structure supporting significant modifications that weren't planned when the system was first conceived.

Software that runs only on a developer's machine isn't providing value to the customers of the software. Traditionally releasing software has been a long and complicated process, one that hinders the need to evolve software quickly. Continuous Delivery uses automation and collaborative workflows to remove this bottleneck, allowing teams to release software as often as the customers demand. For Continuous Delivery to be possible, we need to build in a solid foundation of Testing, with a range of automated tests that can give us confidence that our changes haven't introduced any bugs. This leads us to integrate testing into programming, which can act to improve our architecture.

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Cape Cod, MA (2017)

Data Management

There are many kinds of software out there, the kind I'm primarily engaged is Enterprise Applications. One of the enduring problems we need to tackle in this world is data management. The aspects of data managment I've focused on here are how to migrate data stores as their applications respond to changing needs, coping with different contexts across a large enterprise, the role of NoSQL databases, and the broader issues of coping with data that is both Big and Messy.

Domain-Specific Languages

A common problem in complex software systems is how to capture complicated domain logic in a way that programmers can both easily manipulate and also easily communicate to domain experts. Domain-Specific Languages (DSLs) create a custom language for a particular problem, either with custom parsers or by conventions within a host language.

Books

I've written seven books on software development, including Refactoring, Patterns of Enterprise Application Architecture, and UML Distilled. I'm also the editor of a signature series for Addison-Wesley that includes five jolt award winners.

My Books Page...

Conference Talks

I'm often asked to give talks at conferences, from which I've inferred that I'm a pretty good speaker - which is ironic since I really hate giving talks. You can form your own opinion of my talks by watching videos of some my conference talks.

My Videos Page...

Board Games

I've long been a fan of board games, I enjoy a game that fully occupies my mind, clearing out all the serious thoughts for a bit, while enjoying the company of good friends. Modern board games saw dramatic improvement in the 1990's with the rise of Eurogames, and I expect many people would be surprised if they haven't tried any of this new generation. I also appear regularly on Heavy Cardboard.

My Board Games page...

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Recent Changes

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Code samples for the opening chapter of Refactoring

Fri 15 Mar 2024 11:04 EDT

From time to time people ask me for a copy of the code I used in the opening chapter of Refactoring, so they can follow along themselves. I had Reasons for not providing this code, specifically laziness. Fortunately Emily Bache is more dedicated, and she has set up a github repository - the Theatrical Players Refactoring Kata - with the code, and enough tests to make it reasonable to do the refactoring.

The repository goes further than this, however, in that it includes similar sample code in a dozen languages, including C, Java, Rust, and Python.

She has recently posted a video to her YouTube channel, which outlines why she encourages folks to use this code while they are reading that chapter. Her channel includes a lot of videos on good code technique, and she has a Patreon for readers to support her work.


Measuring Developer Productivity via Humans

Tue 12 Mar 2024 09:36 EDT

Measuring developer productivity is a difficult challenge. Conventional metrics focused on development cycle time and throughput are limited, and there aren't obvious answers for where else to turn. Qualitative metrics offer a powerful way to measure and understand developer productivity using data derived from developers themselves. Abi Noda and Tim Cochran begin their discussion by explaining what a qualitative metric is and why we shouldn't reject them for being subjective or unreliable.

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What if we rotate pairs every day?

Wed 06 Mar 2024 10:33 EST

When pair programming, it's important to rotate the pairs frequently, but many organizations that do pair programming are reluctant to do that. Gabriel Robaina and Kieran Murphy ask the question: “What if we rotate pairs every day?” and worked with three teams through an exercise of daily pair rotation. They developed a lightweight methodology to help teams reflect on the benefits and challenges of pairing and how to solve them. Initial fears were overcome and teams discovered the benefits of frequently rotating pairs. They learned that pair swapping frequently greatly enhances the benefits of pairing. Their article shares the methodology they developed, their observations, and some common fears and insights shared by the participating team members.

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Patterns of Legacy Displacement: Event Interception

Tue 05 Mar 2024 10:03 EST

When we gradually replace a legacy system, we have plenty of cases where the legacy system and its replacement need to interact. Since these legacy systems are often difficult, and costly, to change, we need a mechanism that can integrate elements of the replacement while minimizing the impact to the legacy system. Ian Cartwright, Rob Horn, and James Lewis explain how we can use Event Interception on state-changing events, allowing us to forward them to the replacement.

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Bliki: Periodic Face-to-Face

Tue 27 Feb 2024 09:17 EST

Improvements in communications technology have led an increasing number of teams that work in a Remote-First style, a trend that was boosted by the forced isolation of Covid-19 pandemic. But a team that operates remotely still benefits from face-to-face gatherings, and should do them every few months.

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