SIPOC

It's an extension of the IPO Flow Model by identifying the Supplier (S) providing the inputs and the Customer (C) receiving the outputs. The purpose is to identify the required inputs and all possible sources providing those inputs, to identify the high-level critical steps in the business process, and to identify the ultimate customer or receiver of the outputs created by the process. Altogether it helps visualize the relationship of the entire process from the Supplier to the Customer. Some people prefer to reverse it instead and follow a COPIS as a way of starting with the customer and working backwards.
Related StatStuff Video: 
   -Section 4-Define Phase, Lesson #5 - Building a SIPOC