Exam 2 - Chapter 4
In the Entity-Relationship data model, all instances of an entity of a given type are grouped into: A) entity objects. B) class objects. C) entity classes. D) identifiers. E) entity attributes.
Answer: C
Microsoft Access can be used to build a prototype database, which allows users: A) to draw a crow's foot E-R diagram themselves. B) to normalize the tables in the E-R diagram. C) to validate the data model by demonstrating the consequences of data modeling decisions. D) to determine the functional dependencies in the data model. E) to determine the appropriate primary and foreign keys in the data model.
Answer: C
Microsoft Access is a good tool for creating mock-ups of forms and reports because: A) the form and report generators do not exist within Access itself. B) Access forms and reports are very simplistic. C) Access wizards make it easy to create the forms and reports. D) Access has a version of Microsoft PowerPoint built into it to allow easy creation of PowerPoint slide shows. E) Access has a version of Microsoft Excel built into it to allow easy exporting of data to spreadsheets.
Answer: C
The representation of the content, relationships, and constraints of the data needed to support the system requirements is the: A) relation design. B) implementation. C) data model. D) data view. E) application program.
Answer: C
Whether or not an instance of one entity class must participate in a relationship with another entity class is indicated by the: A) degree. B) recursive cardinality. C) minimum cardinality. D) maximum cardinality. E) ordinality.
Answer: C
Which of the following is true about identifiers of entities? A) Identifiers must be unique. B) Identifiers are not normally used in a naming role. C) The value of an identifier may identify a set of entity instances. D) Identifiers may not be more than two attributes. E) An identifier in the E-R model is equivalent to a key in the relational model.
Answer: C
Which of the following would not be contained in a use case? A) Inputs provided to the system to perform a task B) A description of a task the user wants to perform C) A prototype of the system performing a given task D) Outputs generated by the system in performing a given task E) All of the above would be contained in a use case.
Answer: C
In crow's foot style E-R diagrams, a crow's foot mark on the relationship line near an entity indicates: A) a minimum cardinality of zero. B) a minimum cardinality of one. C) a maximum cardinality of one. D) a maximum cardinality of many. E) Both B and C
Answer: D
In crow's foot style E-R diagrams, a single entity together with a related set of entities that each contain specific sets of attributes related to the single entity represent: A) a strong entity relationship. B) an ID-dependent weak entity relationship. C) a non-ID-dependent weak entity relationship. D) a supertype / subtype relationship. E) a recursive entity relationship.
Answer: D
The number of entity classes involved in a relationship is known as the relationship's: A) maximum cardinality. B) minimum cardinality. C) ordinality. D) degree. E) class.
Answer: D
Which of the following is not a basic element of the E-R Model? A) Identifiers B) Entities C) Cardinalities D) Use cases E) Relationships
Answer: D
A dashed line between entities indicates: A) a unique identifier. B) a minimum cardinality of zero. C) a minimum cardinality of one. D) an identifying relationship. E) a nonidentifying relationship.
Answer: E
An ID-dependent entity is: A) a special type of weak entity. B) an entity in which the identifier of the entity includes the identifier of another entity. C) a strong entity. D) an entity with a maximum cardinality of one. E) Both A and B
Answer: E
In crow's foot style E-R diagrams, a hash mark across the relationship line near an entity indicates: A) a minimum cardinality of zero. B) a minimum cardinality of one. C) a maximum cardinality of one. D) a maximum cardinality of many. E) Both B and C
Answer: E
Microsoft Access can be used to prototype databases for which of the following DBMS products? A) Microsoft Access B) SQL Server C) MySQL D) Oracle Database E) All of the above
Answer: E
Which of the following is not a source for user requirements during the requirements analysis stage of developing a database system? A) Business rules B) User interviews C) Forms D) Use cases E) All of the above are sources for user requirements.
Answer: E
During the design phase of developing a database system, the users are asked about the need for changes to existing forms and reports.
Answer: FALSE
During the implementation phase of developing a database system, the data model is transformed into a database design.
Answer: FALSE
In crow's foot E-R notation, the crow's foot indicates a maximum cardinality of one.
Answer: FALSE
Maximum cardinality indicates whether or not an instance of one entity class must be related to at least one instance of another entity class.
Answer: FALSE
Microsoft Access 2013 is only used to prototype databases where Microsoft Access itself will be the final DBMS.
Answer: FALSE
One type of strong entity is the ID-dependent entity.
Answer: FALSE
System requirements as documented by use cases, business rules, forms, reports, and queries are sufficient to design the database without using a formal data model.
Answer: FALSE
The PRODUCT entity instance is the collection of all PRODUCT entity classes.
Answer: FALSE
The number of entity classes involved in a relationship is the cardinality of the relationship.
Answer: FALSE
Unified Modeling Language (UML) has quickly replaced the E-R Model as the most popular technique for creating data models.
Answer: FALSE
There is usually only one instance of an entity in an entity class.
Answer: FALSE Diff: 1 Page Ref: 247-248
________ can be used to build prototype databases.
Answer: Microsoft Access 2013
A use case is a description of the way a user will employ the features and functions of the new system.
Answer: TRUE
An entity class is described by the structure of the entities in that class.
Answer: TRUE
An entity identifier can be either unique or nonunique.
Answer: TRUE
In crow's foot E-R notation, a circle indicates a minimum cardinality of zero.
Answer: TRUE
In crow's foot E-R notation, the hash mark indicates both a minimum cardinality of one and a maximum cardinality of one.
Answer: TRUE
It is possible for an entity to have a relationship to itself.
Answer: TRUE
Microsoft Access 2013 can be used to build a prototype database, which allows users to validate the data model by demonstrating the consequences of data modeling decisions.
Answer: TRUE
Microsoft Access 2013 database files can be easily copied to create multiple copies of a database.
Answer: TRUE
Microsoft Access 2013 uses banded form and report editors.
Answer: TRUE
Microsoft Access 2013 wizards allow easy mock-ups of forms and reports for prototyping.
Answer: TRUE
Subtype entities may be either exclusive or inclusive.
Answer: TRUE
The E-R Model assumes that all instances of a given entity class have the same attributes.
Answer: TRUE
Use cases can be used to validate the data model, design, and implementation.
Answer: TRUE
When developing a database system, the database is constructed during the implementation phase.
Answer: TRUE
________ are descriptions of the ways users will employ the features and functions of the new information system.
Answer: Use cases
Microsoft Access 2013 uses ________ form and report editors.
Answer: banded
Relationships with the degree 2 are often called ________ relationships.
Answer: binary
Identifiers of an entity that are composed of two or more attributes are called ________ identifiers.
Answer: composite
Microsoft Access 2013 database files can be easily ________ to create multiple copies of a database.
Answer: copied
The ________ is a representation of the content, relationships, and constraints of the data needed to support the system requirements.
Answer: data model
Recursive relationships occur when an entity has a relationship with ________.
Answer: itself
Microsoft Access 2013 can be used to prototype databases for ________.
Answer: many DBMS products
A(n) ________ is a working demonstration of selected portions of the future system.
Answer: prototype
In crow's foot style E-R diagrams, an entity class is represented by a(n) ________.
Answer: rectangle
When an entity class has a relationship with itself, it is called a(n) ________ relationship.
Answer: recursive
An entity that must logically depend on another entity is called a(n) ________ entity.
Answer: weak
Microsoft Access 2013 ________ allow easy mock-ups of forms and reports for prototyping.
Answer: wizards
What is a "use case" and how is it used?
A use case is a description of the way users will employ the features and functions of the new information system. Typically, a use case will include descriptions of the user's work environment, the task to be performed, and how the system would be used to support these tasks. The use case also specifies the inputs and outputs necessary to complete these tasks. The use case is used to document requirements, and validate the data model, design, and implementation.
Distinguish between an entity class and an entity instance.
An entity class is the collection of all entities of a given type. The entity class is described by the structure of the entities in that class. An entity instance is a representation of a particular entity within the entity class. The entity instance is described by the values of the attributes of the entity. An entity class, then, is a collection containing many entity instances.
Distinguish between entity identifiers and keys.
An entity identifier is an attribute or group of attributes that the users use to name or identify instances of an entity class. Unlike a key in the relational model, an entity identifier is more of a logical concept. It is simply an attribute that the users think of as distinguishing between entity instances in their environment. Also, entity identifiers may be unique or non-unique while keys must be unique. If an entity identifier is unique it will identify a single instance of the entity class. If the identifier is non-unique it will identify a set of instances of the entity class.
In crow's foot style E-R diagrams, a circle across the relationship line near an entity indicates: A) a minimum cardinality of zero. B) a minimum cardinality of one. C) a maximum cardinality of one. D) a maximum cardinality of many. E) Both B and C
Answer: A
The Microsoft Access 2013 form editor is a(n): A) banded form editor. B) wizard-based form editor. C) ASCII form editor. D) WYSIWYG form editor. E) Web-based form editor.
Answer: A
The Microsoft Access 2013 report editor is a(n): A) banded report editor. B) wizard-based report editor. C) ASCII report editor. D) WYSIWYG report editor. E) Web-based report editor.
Answer: A
A use case can be used to perform which of the following tasks? A) Transform the data model into the database design B) Validate the data model C) Fill the database with data D) Implement business rules E) Develop applications
Answer: B
Given only the following excerpt of an E-R model: Which of the following is known to be true? A) A single instance of ENTITY A must be related to one instance of ENTITY B. B) Many instances of ENTITY A may be related to one instance of ENTITY B. C) ENTITY B has a degree of many. D) ENTITY B is a weak entity. E) Both A and C are true.
Answer: B
Given only the following excerpt of an E-R model: Which of the following is known to be true? A) There are more instances of ENTITY A than there are instances of ENTITY B in the user's environment. B) A single instance of ENTITY B may be related to many instances of ENTITY A. C) A single instance of ENTITY A must be related to many instances of ENTITY B. D) ENTITY A has a minimum cardinality of one. E) The degree of the relationship is "many."
Answer: B
Which of the following activities is not performed during the implementation phase of developing a database system? A) Filling the database with data B) Transforming the data model into a database design C) Writing application programs D) Creating forms E) Creating reports
Answer: B
Which of the following is not a stage in the development of a database system? A) Requirements analysis B) Validation C) Component design D) Implementation E) All of the above are stages in the development of a database system.
Answer: B
________ constrain data values and the processing of the database.
Answer: Business rules
Explain maximum cardinality
Maximum cardinality describes the maximum number of instances in a given entity class that are allowed to participate in a relationship with a single instance of another entity class. Maximum cardinality is typically represented as being either 1:1 (one-to-one), 1:N (one-to-many), N:1 (many-to-one), or M:N (many-to-many). There is no restriction to only these common values however, and other maximum cardinalities, such as 1:5 (one-to-five) are allowed.
Explain minimum cardinality.
Minimum cardinality describes the minimum number of instances in a given entity class that must participate in a relationship with a single instance of another entity class. The minimum cardinality indicates whether each instance in a given entity class is required to participate in the relationship.
What are "business rules" and what is their role in database design?
The broad definition of a weak entity includes any entity that relies on another entity for its existence in the database. This is ambiguous because this definition can apply to any entity that is involved in a relationship with a minimum cardinality of 1. If the minimum cardinality is 1, then an entity instance in that entity class cannot exist in the database unless there is a related entity instance in the associated entity class. The more restrictive definition of a weak entity indicates that an entity is weak if it logically depends on the other entity for its existence.
Explain the ambiguity in the broad definition of a weak entity.
The broad definition of a weak entity includes any entity that relies on another entity for its existence in the database. This is ambiguous since this definition can apply to any entity that is involved in a relationship with a minimum cardinality of 1. If the minimum cardinality is 1, then an entity instance in that entity class cannot exist in the database unless there is a related entity instance in the associated entity class. The more restrictive definition of a weak entity indicates that an entity is weak if it logically depends on the other entity for its existence.
Distinguish between a data model and a database design.
The data model is a representation of the content, relationships, and constraints of the data needed to support the users' requirements for the system. The data model is a logical representation of business requirements. The database design is created from the data model to include tables, relationships, constraints, data types, column properties, and descriptions of primary and foreign keys. The database design is an implementation design of how database technology can accomplish the support of the system requirements depicted in the data model.
