1. The End User who uses the application. Ultimately, this is the user who actually puts the data in the system into use in business. This user need not know anything about the organization of data in the physical level. She also need not be aware of the complete data in the system. She needs to have access and knowledge of only the data she is using. 2. The Application Programmer who develops the application programs. She has more knowledge about the data and its structure since she has manipulate the data using her programs. She also need not have access and knowledge of the complete data in the system.