3 ms·

If a selected key isn't unique, it's a failure of the data model.

• jacques_chester 14y ago
  It's a failure of clairvoyance, you mean. Reality is more complex than any model. That's why we build models. They are, by their very nature, simpler than reality.
  • jfb 14y ago
    Yeah, true. A model can be valid for some subset of data for some fixed period of time. The real failure is when the model isn't valid even for the defined period. Skill at articulating the limitations and implicit assumptions of any model is far too rare.
    • jacques_chester 14y ago
      That's one thing I found really useful in reading Kimball's books -- the concept of fixed, slowly changing and quickly changing dimensions. Everything is in flux, and you can choose to model that or not model it. At the first level, you just model the current state of the system. Then you begin to model the events that change the current state. Then you begin to model changes in the shape of the problem domain. Models all the way down ...