Quiz
Cierto o falso de Capitulo 4
Questions in this quiz (34)
1E-R models are expressed using a single standardized set of universally accepted symbols.
- ATrue
- BFalse
2An entity is something in the users’ work environment that the users want to track.
- ATrue
- BFalse
3Entities of a given type are grouped into entity classes.
- ATrue
- BFalse
4An entity class is described by the structure of the entities in that class.
- ATrue
- BFalse
5An 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.
- ATrue
- BFalse
6In E-R modeling, entities within an entity class may have different attributes.
- ATrue
- BFalse
7In E-R modeling, an attribute may be either composite or multi-valued, but it cannot be both.
- ATrue
- BFalse
8An identifier of an entity instance must consist of one and only one attribute.
- ATrue
- BFalse
9A “composite identifier” is defined as a composite attribute that is an identifier.
- ATrue
- BFalse
10An identifier may be either unique or nonunique.
- ATrue
- BFalse
11E-R modeling recognizes both relationship classes and relationship instances.
- ATrue
- BFalse
12Relationships do not have attributes.
- ATrue
- BFalse
13A single relationship class involves only one entity class.
- ATrue
- BFalse
14A binary relationship is a relationship based on numerical entity instance identifiers.
- ATrue
- BFalse
15The degree of a relationship is expressed as the relationship’s maximum cardinality.
- ATrue
- BFalse
16A relationship’s minimum cardinality indicates whether or not an entity must be involved in the relationship.
- ATrue
- BFalse
17Relationships among instances of a single entity class are called redundant relationships.
- ATrue
- BFalse
18A weak entity is an entity that cannot exist in the database without (and is logically dependent upon) another type of entity also existing in the database.
- ATrue
- BFalse
19ID-dependent entities are a common type of weak entity.
- ATrue
- BFalse
20All weak entities must have a minimum cardinality of 1 on the entity on which it depends.
- ATrue
- BFalse
21Multi-valued attributes are represented in E-R diagrams by creating a new weak entity to represent the multi-valued attribute and creating a 1:N relationship.
- ATrue
- BFalse
22Subtype entities are used to produce a closer-fitting model when an entity has sets of optional attributes.
- ATrue
- BFalse
23Entities with an IS-A relationship should have the same identifier.
- ATrue
- BFalse
24Inheritance in a generalization hierarchy means that the supertype entity inherits all the attributes of the subtype entity.
- ATrue
- BFalse
25It is not important to document business rules during data modeling since they will be enforced by the application programs.
- ATrue
- BFalse
26UML is intended for modeling and designing object-oriented programs and applications.
- ATrue
- BFalse
27For database design, UML-style E-R diagrams must be treated very differently from traditional E-R diagrams because of their object-oriented background.
- ATrue
- BFalse
28Maximum cardinalities are represented in UML-style E-R diagrams with the same notation (1:1, 1:N, N:M) as in traditional E-R diagrams.
- ATrue
- BFalse
29In UML-style E-R diagrams, a weak entity is shown by placing a filled-in diamond on the parent of the weak entity.
- ATrue
- BFalse
30One weakness of UML-style E-R diagrams is that there is no means of distinguishing between a weak entity that is ID-dependent and a weak entity that is not ID-dependent.
- ATrue
- BFalse
31UML-style E-R diagrams allow for the existence of class attributes, which are attributes that pertain to the collection of all entities within that class not to the individual entity instances
- ATrue
- BFalse
32UML-style E-R diagrams allow for three different levels of visibility of attributes.
- ATrue
- BFalse
33UML-style E-R diagrams introduce object-oriented notation that is of limited practical value in traditional, relational database design.
- ATrue
- BFalse
34The goal of data models is to strive to produce the most accurate model of the real world as possible.
- ATrue
- BFalse
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- #Megasparaalola
- Author
- Angel Perez
- Language
- Español
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