Data modeling is a technique for clearly representing business information structures and rules as input to the database design process. At the heart of data modeling is an appreciation of data as a valuable resource for a business organization. This chapter provides an overview of a methodology for logical data modeling. Recognizing such facts, identifying those that are significant to a user’s business, and developing a corresponding data model enable the user to accommodate access requirements through database technology. Data modeling methodology has several important characteristics that contribute to its effectiveness. The most important constructs within a data model are entities and relationships. A data model, therefore, incorporates numerous rules about the integrity as well as the structure of information used within a business. The data modeling process begins with the definition of a user view or representation of information requirements for one business function, user, or user group.