Manageability - Be Liberal in What You Accept, Conservative in What You Send - The Diigo Meta page

• 25 Apr 07
  

  There's a principle that in effect says that "the higher the degrees of freedom, the more complex the system" (well I don't know who said this). Anyway, it's more complicated to write an implementation based on a "liberal" specification, than one that ...

  interopérabilité

• 25 May 05
  

  Nick Gall

  Nice comparison by Carlos E. Perez of Postel's Robustness Principle to a principle by Bertrand Meyer (of OO fame?).
  

  via_delicious_20101217 ImportedFurl20071006 pinboardimport20141106 Internet

  • Betrand Meyer defined something similar, but more formally:   1. An overriding method may [only] weaken the precondition. This means that the overriding precondition should be logically "or-ed" with the overridden precondition.  2. An overriding method may [only] strengthen the postcondition. This means that the overriding postcondition should be logically "and-ed" with the overridden postcondition.  3. A derived class invariant should be logically "and-ed" with its base class invariant.   In essence, implementations may relax the requirements on its inputs and can be stricter on the conditions of its outputs. Jon Postel gave a general guideline, Meyer applied it to design by contract, the principle holds true for interoperable design.

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