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CHAPTER FIVE DATA MODELING WITH THE ENTITY-RELATIONSHIP MODEL True-False Questions 1. A data model is a plan for a database design. Answer: True Page: 120 2. An entity is something in the users' work environment that the users want to track. Answer: True Page: 120 3. Entities of a given type are grouped into entity classes. Answer: True Page: 120 4. An entity class is described by the structure of the entities in that class. Answer: True Page: 120 5 An entity instance of an entity class is the representation of a particular entity and is described by the values of the attributes of the entity. Answer: True Page: 120 6 In E-R modeling, an attribute describe a characteristics of an entity. Answer: True Page: 121 7. In E-R modeling, entities within an entity class may have different attributes. Answer: False Page: 120 8. An identifier of an entity instance must consist of one and only one attribute. Answer: False Page: 122 9. A "composite identifier" is defined as a composite attribute that is an identifier. Answer: False Page: 122 ¶10. An identifier serves the same role for a table that a key does for an entity. Answer: False Page: 122 11. E-R modeling recognizes both relationship classes and relationship instances. Answer: True Page: 122 12. In today's E-R models, attributes of relationships are still used. Answer: False Page: 123 13. A single relationship class involves only one entity class. Page 5-1
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Chapter Five Data Modeling with the Entity-Relationship Model Answer: False Page: 123 14. A binary relationship is a relationship based on numerical entity instance identifiers. Answer: False Page: 123 15. The degree of a relationship is expressed as the relationship's maximum cardinality. Answer: False Page: 123 16. When transforming a data model into a relational design, relationships of all degrees are treated as combinations of binary relationships. Answer: True Page: 123 17. The principle difference between an entity and a table is that you can express a relationship between entities without using foreign keys. Answer: True Page: 124 18. When designing a database, first identify the entities, then determine the attributes, and finally create the relationships. Answer: False Page: 124 19. Relationships are classified by their cardinality. Answer: True Page: 124 20. A relationship's maximum cardinality indicates the maximum number of entities that can participate in the relationship. Answer: False Page: 124 ¶21. In an E-R model, the three types of maximum cardinality are 1:1, 1:N and N:M. Answer: True Page: 124-125 [And see Figure 5-5] 22. In a 1:N relationship, the term parent refers to the N side of the relationship. Answer: False Page: 125 23. A relationship's minimum cardinality indicates whether or not an entity must participate in the relationship. Answer:
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This note was uploaded on 10/21/2008 for the course IE 224 taught by Professor Plebani during the Spring '08 term at Lehigh University .

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