21.  Explain the relationship between entity, entity class, and entity instance.

22.  Explain the difference between attributes and identifiers.

23.  Name and describe three types of binary relationships.

24.  What is the archtetype/instance pattern?

25.  What is a recursive relationship? Give an example not used in the text.

26.  What are the steps for transforming an entity into a table?

27.  Define a surrogate key, describe the ideal primary key and explain how surrogate keys meet this ideal.

28.  Define and discuss data constraints.

29.  In general, how are recursive relationships handled in a database design?

30.  What is a cascading update?