Problem 2 (1 point each, total 18 points) I. For each item below, specify whether the statement is true (T) or false (F). Each Database Management System (DBMS) is based on a Data Model. Database Users may desire to perform conflicting operations at the same time. For example, in an Airline Reservation System, two on-line users may see the last empty seat while trying to reserve a seat on a flight. Concurrency features of a DBMS prevents them from reserving the same seat, therefore avoiding inconsistent database states. In the Entity-Relationship Model (E-R), an Attribute maps an entity to another entity (or a set of entities). A Relationship, on the other hand, maps an entity to a primitive value. Specialization ISA is the result of taking the union of two or more lower-level entity sets to produce a higher-level entity set. It emphasizes the similarity. In the Network Data Model, relationships between record types are implemented by means of Link Types. Since there can be only one Link Type between two Record Types, we do not need to name the Link Types. In the Hierarchical Data Model, AA and many-to-many Link Types are forbidden. In the Hierarchical Data Model, each Record Type has one or more Children Record Types. In the Relational Data Model, the order of attributes is not important. In the Relational Data Model, Referential Integrity Constraint is a special kind/case of Foreign Key Constraint. Multiple Inheritance happens when a class has more than one sub-class. This problem can be observed in Programming Languages as well. Given two relations named A and B, if we O-JOIN A and B, the maximum number of attributes in the result relation could be (the number of attributes of A) times(*) the number of attributes of B). * in an SQL SELECT statement means "all the tuples. In relational algebra, Cartesian Product (x) can be implemented using the O-JOIN operator. Cartesian Product ISA O-JOIN where 0-condition always evaluates to true. SQL is based on Predicate Calculus. A query in SQL always specifies what should be included in the query result