Contract First Design

http://www.scrum-breakfast.com/2013/06/xm-principle-4-contract-first-design.html

This means design the interface between modules first - not the modules themselves.

When designing a solution:

• Design the interfaces based on outside parameters, e.g. load factors, or communication and power requirements.
• Only architect the connections up front, not the individual components.
• Leave room to grow, i.e. over engineer these interfaces, because changing these fundamental contracts may be expensive.