Domain-Driven Design: Tackling Complexity in the Heart of Software

Chapter Eight. Breakthrough
The returns from refactoring are not linear. Usually there is a marginal return for a small effort,
and the small improvements add up. They fight entropy, and they are the frontline protection
against a fossilized legacy. But some of the most important insights come abruptly and send a
shock through the project.
Slowly but surely, the team assimilates knowledge and crunches it into a model. Deep models can
emerge gradually through a sequence of small refactorings, an object at a time: a tweaked
association here, a shifted responsibility there.
Often, though, continuous refactoring prepares the way for something less orderly. Each
refinement of code and model gives developers a clearer view. This clarity creates the potential for
a breakthrough of insights. A rush of change leads to a model that corresponds on a deeper level
to the realities and priorities of the users. Versatility and explanatory power suddenly increase
even as complexity evaporates.
This sort of breakthrough is not a technique; it is an event. The challenge lies in recognizing what
is happening and deciding how to deal with it. To convey what this experience feels like, I'll tell a
true story of a project I worked on some years ago, and how we arrived at a very valuable deep
model.
[ Team LiB ]

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[ Team LiB ]
Story of a Breakthrough
After a long New York winter of refactoring, we had arrived at a model that captured some of the
key knowledge of the domain and a design that did some real work for the application. We were
developing a core part of a large application for managing syndicated loans in an investment bank.
When Intel wants to build a billion-dollar factory, they need a loan that is too big for any single
lending company to take on, so the lenders form a 
syndicate
that pools its resources to support a
facility 
(see sidebar). An investment bank usually acts as syndicate leader, co-ordinating
transactions and other services. Our project was to build software to track and support this whole
process.