1. Define the following terms: data model, database schema, database state, DDL, and DML. What is the difference between an initial state and a valid state? Describe the three-schema architecture. Why do we need mappings among schema levels? How do different schema definitign languages support this architecture? What is the difference between logical data independence and physical data independence? Which one is harder to achieve? Why? 2. 3. 4. Part 2: Make an ER diagram for the problem narrative. You may use ER Assistant for your diagrams or you may draw them using the textbook notation then submit in the form of a PDF document. Make an ER diagram that could store information about applications to graduate schools. The following requirements should be represented: . Graduate schools have a name, an address, and a contact email. . Students have a name, a major, and a date of birth. . Students could apply to many graduate schools, but they need not apply to any. . A graduate school can have many students who apply to it, but they need not have For each application, we keep track of the date of the application and the application status. Students have reference letters. Each reference letter has an author, a date, and text. Each reference letter is for one student, but a student could have many reference letters There are recruitment events for students to learn information about graduate schools. Events have a location and a date. at e Graduate schools go to many recruitment events, but need not go to any. A recruitment event can have many graduate schools, and must have at least one graduate school. We keep track of the name of the representative sent to a recruiting event by a graduate school. Students can attend recruitment events, but need not attend any. A recruitment event can have many students attend it, and must have at least one student attending it. . Part 3: Start with the following ER diagram: ooka buys ttle auther publisher phone Modify it to create a new EER diagram. Assume that the following must be represented . A Book could be a Textbook or a Fiction Book. It could be both. It could be neither. .Textbooks have a subject area. . Fiction Books have a time period and a locale. . Customers could be students or faculty. A customer could be someone other than a student or a faculty member. A customer cannot be both student and faculty. Faculty members have an office address, an office phone, and a department. .Students have a major. Students can be further classified into graduate students and undergraduate students. . No student is both undergraduate and graduate. All students are one of these. . Undergraduate students have a class year. . Graduate Students have a degree program and a finish date. Faculty can order textbooks to be used for their courses. A faculty member can order Fiction Books have a time period and a locale Customers could be students or faculty. A customer could be someone other than a student or a faculty member. A customer cadnot be both student and faculty Faculty members have an office address, an office phone, and a department. . - Students have a major. . Students can be further classified into graduate students and undergraduate students. . No student is both undergraduate and graduate. All students are one of these. Undergraduate students have a class year Graduate Students have a degree program and a finish date. Faculty can order textbooks to be used for their courses. A faculty member can order many textbooks, and a textbook can be ordered by many facuity. We keep track of . . the course ID and the order date for each order. Students can rent textbooks. A student can rent many textbooks, and a textbook can be rented by many students. For each textbook rental, we keep track of the rental date and the return date. Graduate students can mentor undergraduate students. An undergraduate student has just one mentor, but a graduate student can mentor many undergraduates