What's wrong with the rational model

  1. We Don’t Really Know the Goal When We Start
  2. We Usually Don’t Know the Decision Tree – We Discover It as We Go
  3. The Nodes Are Really Not Design Decisions, but Tentative Complete Designs
  4. The Goodness Function Cannot be Evaluated Incrementally
  5. The Desiderata and Their Weightings Keep Changing
  6. The Constraints Keep Changing
  1. ​Changing constraints​
  2. ​Deciding what to design​
  3. ​The situation talks back​