User Profiles
Users are differentiated by the way they expect to interact with the system
- Application programmers 
 -  interact with system through DML calls
 
- Sophisticated users 
 -  form requests in a database query language
 
- Specialized users 
 -  write specialized database applications that do not fit into the traditional data processing framework
 
- Naive users 
 -  invoke one of the permanent application programs that have been written previously