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

Figure 14.13. The relative demands of 
CONTEXT
 relationship patterns
When Your Project Is Already Under Way
Most likely, you are not starting a project but are looking to improve a project that is already
under way. In this case, the first step is to define 
BOUNDED CONTEXTS
according to the way things
are now
. This is crucial. To be effective, the 
CONTEXT MAP
must reflect the true practice of the
teams, 
not
the ideal organization you might decide on by following the guidelines just described.
Once you have delineated your true current 
BOUNDED CONTEXTS
and described the relationships
they currently have, the next step is to tighten up the team's practices 
around that current
organization
. Improve your 
CONTINUOUS INTEGRATION
within the 
CONTEXTS
. Refactor any stray
translation code into your 
ANTICORRUPTION LAYERS
. Name the existing 
BOUNDED CONTEXTS
and make
sure they are in the 
UBIQUITOUS LANGUAGE
of the project.
Now you are ready to consider changes to the boundaries and relationships themselves. These

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changes will naturally be driven by the same principles I've already described for a new project,
but they will have to be bitten off in small pieces, chosen pragmatically to give the most value for
the least effort and disruption.
The next section discusses how to go about actually making changes to your 
CONTEXT
boundaries
once you have decided to.
[ Team LiB ]

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[ Team LiB ]
Transformations
Like any other aspect of modeling and design, decisions about 
BOUNDED CONTEXTS
are not
irrevocable. Inevitably, there will be many cases in which you have to change your initial decision
about the boundaries and relationships between 
BOUNDED CONTEXTS
. Generally speaking, breaking
up 
CONTEXTS
is pretty easy, but merging them or changing the relationships between them is
challenging. I'll describe a few representative changes that are difficult yet important. These
transformations are usually much too big to be taken in a single refactoring or possibly even in a
single project iteration. For that reason, I've outlined game plans for making these
transformations as a series of manageable steps. These are, of course, guidelines that you will
have to adapt to your particular circumstances and events.