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Design perfume

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Design perfume

  1. 1. Design Perfume The sweet smells of quality
  2. 2. Supple <ul><li>Rigidity  - System is hard to change. </li></ul><ul><li>The system is easy to change: </li></ul><ul><ul><li>introduce new modules </li></ul></ul><ul><ul><li>substitute alternate implementations </li></ul></ul><ul><ul><li>substitute alternate technologies  </li></ul></ul><ul><ul><li>extend with new functionality </li></ul></ul><ul><ul><li>refactor for clearer design  </li></ul></ul>
  3. 3. Resilient  <ul><li>Fragility  - Changes cause the system to break easily and require other changes. </li></ul><ul><li>Problems and their solutions tend to stay localised: </li></ul><ul><ul><li>Failures don't bring whole systems down </li></ul></ul><ul><ul><li>Failures don't introduce bad data </li></ul></ul><ul><ul><li>Bad data doesn't propagate </li></ul></ul><ul><ul><li>The consequences of failure make sense given the causes  </li></ul></ul><ul><ul><li>Fixes stay localised  </li></ul></ul><ul><ul><li>Technologies is used in obvious and limited scopes </li></ul></ul><ul><ul><li>Dependencies on specific configurations are localised </li></ul></ul>
  4. 4. Re-usable <ul><li>Immobility  - Difficult to disentangle components that can be reused in other systems. </li></ul><ul><li>Just fits in anywhere it might be useful: </li></ul><ul><ul><li>Any dependencies should make sense </li></ul></ul><ul><ul><li>Configuration and maintenance should be proportionate  </li></ul></ul><ul><ul><ul><li>Easy to figure out </li></ul></ul></ul><ul><ul><ul><li>Sensible defaults </li></ul></ul></ul><ul><ul><ul><li>Updates should seem relevant and not a burden  </li></ul></ul></ul><ul><ul><li>Reuse should add clarity: </li></ul></ul><ul><ul><ul><li>Making the intention and correct use obvious </li></ul></ul></ul><ul><ul><ul><li>Not introducing too much unused functionality  </li></ul></ul></ul>
  5. 5. Enabling  <ul><li>Viscosity  - Doing things right is harder than doing things wrong. </li></ul><ul><li>Makes good practices easy: </li></ul><ul><ul><li>The right information and operations are available  </li></ul></ul><ul><ul><ul><li>Back doors are hard find or make </li></ul></ul></ul><ul><ul><ul><li>It's easy to find or do what you need </li></ul></ul></ul><ul><ul><li>Like Guice makes DI easier than calling new </li></ul></ul><ul><ul><li>Like list processing libraries lead to less error prone loops, and more explicit condition and operation objects </li></ul></ul>
  6. 6. Appropriately Complex <ul><li>Needless Complexity  - System contains infrastructure that has no direct benefit. </li></ul><ul><li>The reasons for complexity are obvious: </li></ul><ul><ul><li>Clearly connecting complexity to business needs </li></ul></ul><ul><ul><ul><li>Thinking about the complexity reveals important things </li></ul></ul></ul><ul><ul><li>Complexity is visible up front </li></ul></ul><ul><ul><ul><li>No nasty surprises when you start to dig in </li></ul></ul></ul><ul><ul><ul><li>Complexity hiding shouldn't produce time-bombs </li></ul></ul></ul>
  7. 7. DRY <ul><li>Needless Repetition  - Repeated structures that should have a single abstraction. </li></ul><ul><li>Don't Repeat Yourself </li></ul><ul><li>Don't force users of your code to repeat themselves: </li></ul><ul><ul><li>Good default values or reusable configuration </li></ul></ul><ul><ul><li>Useful state and memory of previous actions </li></ul></ul><ul><ul><li>No need to code up the same things repeatedly </li></ul></ul>
  8. 8. Transparent <ul><li>Opacity  - Code is hard to understand. </li></ul><ul><li>Good code is obvious and easy to understand:  </li></ul><ul><ul><li>It does what it says it does </li></ul></ul><ul><ul><li>It doesn't do extra unexpected stuff  </li></ul></ul><ul><ul><ul><li>Explicit consequences (not implicit) </li></ul></ul></ul><ul><ul><li>It matches reasonable expectations </li></ul></ul>
  9. 9. Manifesto-style <ul><li>We prefer to strive toward excellence  </li></ul><ul><li>over  </li></ul><ul><li>merely struggling away from mediocrity. </li></ul>

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