In this chapter, we continue the discussions in Chap. 1. Step by step, we built the mathematical background of the requirement axioms to measure the performance of homogenous firms. We similarly start with a question from the gemstone company and gradually illustrate the new concepts. The provided concepts are not new, and have been mentioned in the literature of operations research; however, in order to avoid any confusion and pretend judgment based on the literature, only the concepts are re-introduced and the pros and cons of each concept are demonstrated. We also provide a philosophical argument to clarify some of the concepts. At the end of this chapter, readers will have an understanding of the overall concepts used to measure the performance of firms and will be ready to develop the mathematical background for complex situations.