See KentBeck and DaveCleal on Optional Scope Contracts:

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Anyone able to pull this off successfully (other than RoleModelSoftware)?

''Yes, QuinarySpa'' --PiergiulianoBossi

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What if I do not want to join yahoo.com to fin out about Optional Scope Contracts?  --CarlNelson

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Ron Jeffries was kind enough to host the PDF here: 
*** http://xprogramming.com/articles/optional-scope-contracts/