دانلود کتاب تحول مبتنی بر دامنه -مدرن‌سازی سیستم‌های قدیمی و کاهش ریسک

“All happy families are alike; each unhappy family is unhappy in its own way.” This Anna Karenina principle applies not only to families, but also to legacy software development teams. Different software systems suffer from different “diseases,” and from this comes the need for a variety of remedies to cure them all. We have observed the following diseases in various combinations in legacy systems—whether monoliths or microservices—and their organizations in recent years: The legacy system has become a big ball of mud1 because no one controlled the dependencies and now everything is connected to everything else (Chapter 5). The domain knowledge is entangled into one huge domain model whose parts fit together only partially or even contradict each other (unbounded models in Chapter 12). Business source code and technical source code are mixed, and thus the replacement of obsolete technology or a domain extension becomes a Herculean task (Chapter 8). People are organized in a team structure that is unsuitable for making fast progress (Chapter 9). On the cover of this book you can see an Atlas moth. Just like the legacy systems in this book, it has begun as something small (an egg), then developed into something bulky and clumsy (a caterpillar) and further into a big ball (a silken cocoon), and finally transforms into something beautiful and spreads its wings to fly into a promising future. Another similarity between insect and legacy system is the size; the Atlas moth is one of the largest moth species in the world with a wingspan of 9–10 inches. In this book, we present the treatments for these diseases that we have learned over the past 20 years working with Domain-Driven Design (DDD) and legacy software. These include: refactorings, Domain Storytelling, EventStorming, Team Topologies, and the Modularity Maturity Index (MMI). When we approach the healing in our own projects and with our customers, the respective development team looks significantly more positively into the future and motivation increases. The further the healing progresses, the happier users, project leaders, and managers will also be because the stodgy and expensive legacy software becomes more stable, can be adapted more quickly, and ultimately even allows innovative, forward-looking enhancements (again).