There are four different types of database system users, differentiated by the way that they expect to interact with the system. A primary goal of a database system is to provide an environment for retrieving information from and storing new information into the database.
- Application programmers: They are computer professionals who interact with the system through DML calls, which are embedded in a program written in a host language (for example COBOL, C). Since the DML syntax is different from the host language syntax, DML calls are usually prefaced by a special character so that the appropriate code can be generated. A special preprocessor, called the DML precompiler, converts the DML statements to normal procedure calls in the host language. There are special types of programming languages that combine control structures of Pascal like languages with control structures for the manipulation of a database object.
- Sophisticated users: Sophisticated users interact with the system without writing programs. Instead, they form their requests in a database query language. Each such query is submitted to a query processor whose function is to break down DML statement into instructions that the storage manager understands.
- Specialised users: Specialised users are sophisticated users who write specialised database applications that do not fit into the traditional data-processing framework. Among these applications are computer aided design systems, knowledge-base and expert systems.
- Native users: Native users are unsophisticated users who interact with the system by invoking one of the permanent application programs that have been written previously.
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