18. Consider the relation schema CLASS with attributes Student, Subject, and Teacher. The meaning of this relation is that the specified student is taught the specified subject by the specified teacher. Assume that semantic rules depicted by the following functional dependecies, exist:

{Student, Subject} -> Teacher

Teacher -> Subject

Subject -/->

{Student, Teacher} -> Subject

a. What do these rules mean in words? Are all these rules necessary? If not, explain which are not needed?

b. Is the following sample data consisten with these rules? Why or why not? (SEE SAMPLE ABOVE)

c. What causes CLASS to contain a BCNF violation? What anomalies does it exhibit?

d. Decompose CLASS if necessary so that resulting relational schema is in BCNF. Is your design attribute-preserving, dependecy-preserving, and a lossless-join decomposition? Explain.

Normal Forms Based on Functional Dependencies 18. Consider the relation schema CLAss with attributes student, subject, and Teacher. The meaning of this relation is that the specified student is taught the specified subject by the specified teacher. Assume that semantic rules, depicted by the following functional depen- dencies, exist: (Student, Subject) Teacher Teacher Subject Subject Teacher Student, Teacher) Subject a. What do these rules mean in words? Are all the rules necessary? If not, explain which are not needed. b. Is the following sample data consistent with these rules? Why or why not? Student Subject Teacher Smith Math White Physics Smith Green Math White Jones Physics Brown Jones c. What causes CLASS to contain a BCNF violation? What anomalies does it exhibit? d. Decompose CLASS if necessary so that the resulting relational schema is in BCNF. Is your design attribute-preserving, dependency-preserving, and a lossless-join decompo- sition? Explain