Design Facts

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Design Facts

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Reference

• Facts and Fallacies of Software Engineering by
  Robert L. Glass, Addison-Wesley, 2003, ISBN
  0-321-11742-5

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Design Fact 26

• When moving from requirements to design, there is
  an explosion of derived requirements (the
  requirements for a particular design solution)
  caused by the complexity of the solution process.
  The list of these design requirements is often
  50 times longer than the list of original
  requirements.

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Derived Requirements

• Often the reason it is difficult to implement
  requirements traceability even though everyone
  agrees it is important to do so.
• Simple design solutions are always sought, but
  only rarely found.
• What if a requirement links to 50 or more design
  requirements?
• The author can remember telling his software
  engineering students this in the early 1980s.

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Design Fact 27

• There is seldom one best design solution to a
  software problem.

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One and Best

• Most software problems can be solved in many
  different ways.
• It is extremely difficult to know whether you
  have found a best solution even if there were
  one.
• You can certainly compare two solutions and find
  one better than another. But this comparison can
  be extensive and difficult.
• Again, dont let simple degenerate into
  simplistic

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Design Fact 28

• Design is a complex, iterative process. The
  initial design solution will likely be wrong and
  certainly not optimal.

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Hard Part First

• Top designers pursue a design solution by
  pursuing targets of important opportunity.
• Those targets of important opportunity are
  usually the difficult problems. You must
  eliminate these if a final solution is to be
  created.