Building Evolutionary Architectures: Support Constant Change 1st Edition Pdf

For a long time, the software industry followed the notion that architecture was
something that ought to be developed and completed before writing the first line of
code. Inspired by the construction industry, it was felt that the sign of a successful
software architecture was something that didn’t need to change during development,
often a reaction to the high costs of scrap and rework that would occur due to a rearchitecture
event.



This vision of architecture was rudely challenged by the rise of agile software methods.
The pre-planned architecture approach was founded on the notion that requirements
should also be fixed before coding began, leading to a phased (or waterfall)
approach where requirements was followed by architecture which itself was followed
by construction (programming). The agile world, however, challenged the very
notion of fixed requirements, observing that regular changes in requirements were a
business necessity in the modern world, and providing project planning techniques
to embrace controlled change.
In this new agile world, many people questioned the role of architecture. And certainly
the pre-planned architecture vision couldn’t fit in with modern dynamism. But
there is another approach to architecture, one that embraces change in the agile manner.
In this view architecture is an constant effort, one that works closely with programming
so that architecture can react both to changing requirements but also to
feedback from programming. We’ve come to call this evolutionary architecture, to
highlight that while the changes are unpredictable, the architecture can still move in a
good direction.
At ThoughtWorks, we’ve been immersed in this architectural world-view. Rebecca led
many of our most important projects in the early years of this millenium, and developed
our technical leadership as our CTO. Neal has been a careful observer of our
work, synthesizing and conveying the lessons we’ve learned. Pat has combined his
project work with developing our technical leads. We’ve always felt that architecture
is vitally important, and can’t be left to idle chance. We’ve made mistakes, but learned respond gracefully to the many changes in its purpose.
The heart of doing evolutionary architecture is to make small changes, and put in
feedback loops that allow everyone to learn from how the system is developing. The
rise of Continuous Delivery has been a crucial enabling factor in making evolutionary
architecture practical. The authorial trio use the notion of fitness functions to monitor
the state of the architecture. They explore different styles of evolvability for architecture,
and put emphasis on the issues around long-lived data—often a topic that
gets neglected. Conway’s Law towers over much of the discussion, as it should.
While I’m sure we have much to learn about doing software architecture in an evolutionary
style, this book marks an essential road map on the current state of understanding.
As more people are realizing the central role of software systems in our
twenty-first century human world, knowing how best to respond to change while
keeping on your feet will be an essential skill for any software leader.
— Martin Fowler
martinfowler.com
September 2017
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