Following on from http://www.eiffelroom.com/blog/colin_adams/correctness_conditions_for_calling_an_agent, I have thought about the following scheme (it would require ECMA to be amended to require a tag on assertions, but this should be done anyway. Also, the tag would have to be unique with all the preconditions for a given feature - likewise for postconditions.):

<eiffel> class ROUTINE

I was recently reading the paper "From Design Patterns to Reusable Components: The Factory Library by Karine Arnout and Bertrand Meyer" and I noticed that although they had succeeded in turning the pattern "Abstract Factory" into a component, the resulting class (ABSTRACT_FACTORY) did not have a sound contract.