The manufacturing enterprises are currently under great pressures to shorten innovation cycles, grow importance of high-efficiency manufacturing and accommodate new products by building more factories. Discrete manufacturing sectors face a huge array of problems because of its specificity. Knowledge representation is one of the most highlighted troubles. In this case, ontology is a significant knowledge model for representing discrete manufacturing knowledge in a human and machine interpretable way. This knowledge can also be used for automatic design-making to reconfigure the control software that supervises and coordinates the production process of discrete manufacturing. This paper addresses the important issues in developing specific ontology for discrete manufacturing. A generic ontology named DeMO is developed considering all the aspects about product from customized order to resulting production.