Database:

PERSON P LNAME P FNAME P IS EMP P IS STU PIS-EMP (0) P-S-STU EMPLOYEE STUDENT EMP HIRE DATE EMP IS ADM EMP IS PROF STU MAJOR STU TYPE EMP IS ADM (O EMP IS_PROF d STU TYPE ADMINISTRATOR PROFESSOR GRADUATE UNDERGRAD PK,FK1 P ID ADM TITLE PROF RANK GRAD THESIS UND HOURS 1. What is a subtype discriminator? Given an example of its use ANS: 2. There two category symbols: overlapping subtype, nonoverlapping subtypes (disjoint subtype) What is an overlapping subtype? Give an example What is a disjoint subtype? Give an example: 3. What is the difference between partial completeness and total completeness