Text: Fundamentals of Database Systems, Elmasri, Ramez; Navathe, Shamkant B.

Chapter: Answer the following questions.

26.34 Consider the COMPANY database described in Figure 5.6 on page 162 of E&N. Using the syntax of Oracle triggers, write the active rules to do the following:

a. Whenever an employee's project assignments are changed, check if the total hours per week spent on the employee's projects are less than 30 or greater than 40; if so, notify the employee's direct supervisor.

Use this command to notify the manager of that an employee has worked more or less hours than expected:

host /usr/sbin/sendmail -t <"Employee " + Essn + " has more or less hours than expected this week">

b. Whenever an employee is deleted, delete the PROJECT tuples and DEPENDENT tuples related to that employee, and if the employee manages a department or supervises employees, set the Mgr_ssn for that department to NULL and set the Super_ssn for those employees to NULL.

26.35 Repeat Exercise 26.34 (prior question) but use the syntax of STARBURST active rules.

26.43 Consider a deductive data base with the following rules:
r1 : ANCESTOR(X, Y) :- FATHER(X, Y)
r2 : ANCESTOR(X, Y) :- FATHER(X, Z), ANCESTOR(Z, Y)
Notice that FATHER(X, Y) means that X is the father of Y; ANCESTOR(X, Y) means that X is the ancestor of Y.

Consider the following fact base:

FATHER(Harry, Issac), FATHER(Issac, John), FATHER(John, Kurt)

a. Construct a model-theoretic interpretation of the above rules using the given facts.

b. Consider that a database contains the above relations FATHER(X, Y), and another relation BROTHER(X,Y), and third relation BIRTH(X, B), where B is the birth date of Person X. State a rule that computes the first cousins of the following variety: their fathers must be brothers