Database design in a relational environment is much easier than with other DB models because the logical design phase is separated from phy- sical design phase. This is the basic principle of provide a fast application development environment. Top down analysis tends to be done with the aid of diagrams where it is easy to identify the critical areas at an early stage. This approach considers the relationships between 'entities'.
Entities are 'things' or 'concepts' about which data is collected.
The entities are described by attributes. The final design usually generates one relation per entity with the attributes becoming columns in relations. This decomposition goes through stages known as 'normal forms'. For many applications, third normal form is sufficient. 20 covers the ER approach.