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97 Things Every Software Architect Should Know by Richard Monson-Haefel

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Chapter 65. Your System Is Legacy; Design for It

Dave Anderson is a principal software engineer at Belfast software company Liberty IT, which supplies IT solutions for Fortune 100 company Liberty Mutual. Dave has more than 10 years' experience in the software industry with many leading-edge IT companies across several different industries and countries.

Dave Anderson
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EVEN IF YOUR SYSTEM IS BLEEDING EDGE and developed in the latest technology, it will be legacy to the next guy. Deal with it! The nature of software today means things go out of date fast. If you expect your system to go into production and survive, even for a few months, then you need to accept that maintenance developers will need to fix things up. This means several things:

  • Clarity: It should be obvious what role components and classes perform.

  • Testability: Is your system easy to verify?

  • Correctness: Do things work as designed or as they should? Eliminate quick and nasty fixes.

  • Traceability: Can Ernie the Emergency Bug Fixer—who has never seen the code before—jump into production, diagnose a fault, and put in a fix? Or does he need an eight-week handover?

Try to think of a different team opening up the codebase and working out what's happening. This is fundamental for great architecture. It doesn't have to be oversimplified or documented to the hilt; a good design will document itself in many ways. The way a system behaves ...

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