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I just realised that I’ve used the term ‘design hypothesis’ throughout this blog without a clear definition of what one is. 🙂

So here it is.

A design hypothesis is a prediction that a specific design will result in a specific outcome. A design hypothesis must:

  1. Identify the designs provenance, e.g the theory, practice or standards from it is derived.
  2. Provide a concise description of the design.
  3. State what the design must achieve in a verifiable fashion.
  4. Clearly identify critical assumptions that support the hypothesis.

Note that the concept of a fault hypothesis can be seen as a particular and constrained form of design hypothesis as, after Powell (1992), a fault hypothesis specifies assumptions about the types of faults, the rate at which components fail and how components may fail for fault tolerant computing purposes.

I give a short example of of a design hypothesis in the Titanic Part I post.

References

Powell, D., Failure mode assumptions and assumption coverage. In Proc. of the 22nd IEEE Annual International Symposium on Fault-Tolerant Computing (FTCS-22) , p386–395, Boston, USA, 1992.

The Titanic effect

27/09/2010

So why did the Titanic sink? The reason highlights the role of implicit design assumptions in complex accidents and the interaction of design with operations of safety critical systems

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