Lean Architecture by Coplien James O. & Bj & #248 & rnvig Gertrud

Author:Coplien, James O. & Bj & #248 & rnvig, Gertrud
Language: eng
Format: epub
Publisher: Wiley
Published: 2010-12-21T16:00:00+00:00

Even the best design can’t flatten the cost curve to a constant: there is always a price to pay for change. One good rule of thumb in answering the “unreasonably costly” question is to apply Meyer’s model in a relative way. Assess the cost of a moderately complex change. If you can find a large set of changes that should be easier from a business context, or from the context of the end user mental model, and that are more expensive than the moderate change, your architecture may not be as good as it should be.

In doing this cost assessment, you should be careful to start by separating architectural costs from operational, training, customer retrofit, and other business costs that don’t trace directly to the architecture. Evaluate the architecture for its own sake. In the end, everything matters, but you want to start by separating concerns; you’ll find that helps clarify subsequent discussions of tradeoffs. Later, the business may recommend a sub-optimal architectural change (e.g., in the interest of embracing a standard that has gained market attention) because the overall business result will be better. Taking a cue from Lean, all decisions should focus on long-term results. Long-term arguments usually, but not always, work in the interest of an elegant architecture. Nerds: sometimes you’ll lose these arguments, and you’ll have to learn to take your medicine and buy into the bigger picture.

There is no good definition of architectural completeness (though we take a stab at it in Section 6.4). A good team is always refining the architecture as requirements become better understood and grow over the product lifetime. Architectures change, and minimizing their surprising costs reduces risk in the product’s profitability. The team needs to agree what “done” means for “the architecture is done” at any given stage in the project.

See also Section 6.2.2, “Testing the relationships.”

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