There are two major types of specification: conformance and performance specifications. They have the following characteristics:

Since performance specification is often a list of outputs or outcomes, it usually takes less time to develop than conformance specification.

For straight re-buy, the specifications for the products are known. Generally, there will be an existing contract with supplier in place. The business need is challenged annually, only on the annual demand. So effective inventory control will help procurement successfully manage straight re-buy.