this chapter has discussed the concepts and the development of data models. first, we talked about the interview process through the case study of Hillcrest Computing. through the interviews with the key players in a business process, the database project and set up the design goals accordingly. to represent the data by a conceptual structure, the concepts of the entity-relationship data model were introduced. the major components, such as entities, attributes, and relationships, in an E-R data model were explained with examples. by examining the business process, the database designer was able to create the entities and the relationship among these entities.