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.

Photostream

Heian-jingu Shrine

Kyoto, Japan (2004)

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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Advocate, educator, and authorial stance

Tue 19 Jul 2022 13:20 EDT

When I'm writing, or mentoring others in writing, about a particular technique I prefer to take the role of an educator rather than that of an advocate. When doing that, I see two main stances an author can take. One is to focus on the trade-offs between this technique and its alternatives, the other is to focus on the merits of the particular technique and not discuss the alternatives.

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Legacy Displacement: Revert to Source

Thu 07 Jul 2022 10:07 EDT

Legacy systems often act as integration hubs, ingesting source data to pass on to downstream systems. A new downstream system can decouple itself from legacy by finding the source of data to the legacy and integrating directly to that instead. Ian Cartwright, Rob Horn, and James Lewis describe this Revert to Source pattern, explaining that this part of legacy displacement often also allows a new system to take advantage of upgrades to source data that the legacy had neglected.

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Product Backlog Building Canvas

Tue 14 Jun 2022 10:15 EDT

Many software teams describe desired product capabilities as a product backlog: a list of user stories. These stories capture who needs the work, what the work is, and why it's needed. Too often teams expect a product owner to be the sole source of the backlog, but anyone could (and should) write user stories. Paulo Caroli teaches teams to use a Product Backlog Building Canvas, which provides a simple process to develop user stories, starting with describing personas for product users and the activities they do. These activities yield features: their interactions with the product. Features are broken down into backlog items, which can then be formulated into user stories from the background of personas and activities.

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Agile Book Club interview on Refactoring

Thu 28 Apr 2022 11:33 EDT

James Shore's Art of Agile Development is my favorite single-volume book on agile software development. A reason for that is its serious emphasis on the technical practices that are essential to making it work effectively. James and I discuss the role of refactoring for software development, the nature of design changes we see, and how to break down big changes into small pieces.

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How I use Twitter

Tue 26 Apr 2022 08:50 EDT

A couple of recent conversations about Twitter were nudging me into writing about how I use Twitter even before The Muskover developed. Twitter has become an important part of my online life, and my online life is a big part of what I do. But like any tool, Twitter can be used in many different ways, and how you use it affects how useful it can be.

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Transitional Architecture

Mon 28 Mar 2022 14:49 EDT

The core to a successful legacy displacement is the gradual replacement of legacy with new software, as this allows benefits to delivered early and circumvents the risks of a Big Bang. During displacement the legacy and new system will have to operate simultaneously allowing behavior to be split between old and new.

Ian Cartwright, Rob Horn, and James Lewis explain how to build and evolve a Transitional Architecture that supports this collaboration as it changes over time. For this to work, intermediate configurations may require integrations that have no place in the target architecture of the new system.

Or to put this more directly - you will have to invest in work that will be thrown away.

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