Dispite effective designs that aim to achieve good data, however, some anomolies are introduced during use of the data.

• Discuss attribute semantics as an informal measure of goodness for a relational schema – that is, ways that attributes and be constructed during conception to achieve good data. Illustrate with example
• Discuss Insertion, Deletion, and modification anomolies. Why are they considered bad? Illustrate with examples.
• Why should NULLs in a relation be avoided as much as possible? Discuss the problem of spurious tuples and how to prevent it.