References

1. A. Silberschatz, H. F. Korth and S. Sudarshan, Database System Concepts, McGraw-Hill, 3rd ed., 1997.
2. J. D. Ullman, ``Principles of Database and Knowledge-Base Systems'', Vol. 1, Computer Science Press, 1988. Chapter 1 ``Data Base, Object Base and Knowledge Base'', Chapter 5. ``Object-Oriented Database Languages''.
3. R. Elmasri and S. B. Navathe, Fundamentals of Database Systems, Bemjamin/Cummings, 2nd ed. 1994.