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AIS Exam#2

data
Stored representations of objects and events that have meaning and importance in the user’s environment.
examples of data
facts, text, graphics, images, etc.
Information
*Data* that have been *processed* in such a way as to *increase* the *knowledge of* the person *who uses* the data.
*Metadata*
*”data about data.”*

Data that describe the properties or characteristics of end-user data and the context of those data.

Database application
An application program, (or set of related programs), that is used to perform a series of database activities, (such as create, read, update, and delete), on behalf of database users.
*File Processing System*
*= a paper system*
*Problems with File Processing system*
*Redundancy*.

*Inconsistency*: a change in a file in one department will not be the same in another department.

Traditional File Processing Systems
*No databases*.

*Computer file processing systems.*

Computers store, manipulate, and retrieve large files of data.

Disadvantages of File Processing Systems
1. Program-data dependence.

2. Duplication of data.

3. Limited data sharing.

4. Lengthy development times.

5. Excessive program maintenance.

Program-data dependence
*File descriptions are stored within each program*.

*Any change to a file* structure *requires changes to* the file descriptions for *ALL programs* that access that file.

Program-data Independence
*Data descriptions are stored in a central location, (repository).*

Allows data to change without changing the programs that process that data.

Limited data sharing
*Each application has its own private files.*

*File incompatibility between applications.*

Users have limited ability to share data outside of their own applications.

Difficult to draw data: need to draw several incompatible files from separate systems.

Improved data sharing
One unified database.

Multiple users have access to data in the database via different user views.

Users can easily share data.

Data model
Graphical systems used to capture the nature and relationships among data.
Data models
Are made up of *entities*, *attributes*, and *relationships*.
Relational database
A database that represents data as a collection of tables in which all data relationships are represented by common values in related tables.
*SQL*
*Structured Query Language.*
*DBMS*
*Database Management System*.

*NOT a database, it is a software.*

Database management system
A software system that is used to create, maintain, and provide controlled access to user databases.
How does *DBMS* function?
It enables end users & application programmers to share data,

and,

it enables data to be shared among multiple applications.

Systems Development Life Cycle (SDLC)
The traditional methodology, or *steps*, used to develop, maintain, and replace *information systems*.
What are the steps in SDLC?
1. Planning.

2. Analysis.

3. Design.

4. Implementation.

5. Maintenance.

ERD
*Entity-Relationship Diagram* (E-R diagram).

A graphical representation of an entity-relationship model.

Business Rules
Statements that define or *constrain* some aspect(s) of the business.

They are intended to assert business structure, or to control, or influence the behavior of the business.

Also known as “integrity constraint”.

Why are Business Rules important?
They help ensure that information systems work right, and that users of the information understand what they enter, and see.
Examples of Business Rules affecting data processing, and data storage.
“A student may register for a section of a course only if he or she has successfully completed the prerequisites for that course.”

“A preferred customer qualifies for a 10 percent discount, unless he has an overdue account balance.”

Entity
A *person*, a *place*, an *object*, an *event*, or a *concept* in the user environment about which the organization wishes to maintain data.
Entity type
A collection of entities that share common properties or characteristics.

For example, *EMPLOYEE* in a company’s database, represents many employees.

Entity Instance
A single occurrence of an entity type.

For example, employee Joe Diaz, within the “EMPLOYEE” entity type.

Relationship
An association representing an interaction among the instances of on or more entity types that is of interest to the organization.

Relationships & their characteristics: degree, & cardinality, represent business rules.

Relationship type
= cardinality.

A meaningful association between, or among, entity types.

Allow us to answer questions that could not be answered given only the entity types.

Relationship degrees
The number of entity types that participate in a relationship.
3 most common relationship degrees in E-R models:
Degree 1: Unary. One to one.,

Degree 2: Binary. One to Many. Or Many to Many.,

Degree 3: Ternary. Simultaneous among three entity types.

Example of One to One.
person, “is married to”, person.
Example of One to Many.
Employee, “manages”, Employee(s).
Example of Many to Many.
Student(s), “registers for, Course(s).
Composite attributes
Attributes that can be divided into smaller sub-parts.

These sub-parts represent basic attributes with independent meanings of their own.

For example, take Name attributes. We can divide it into sub-parts like First_name, Middle_name, and Last_name.

Derived attributes
Attributes whose values are generated from other stored attributes.

For example, Account Balance is derived by subtracting Total Debit from Total Credit.

Identifier attributes
Called keys or key attributes uniquely identify an instance of an entity.

If such an attribute doesn’t exist naturally, a new attribute is defined for that purpose.

For example, an ID number, or code.

Cardinality constraint
A rule that specifies the number of instances of one entity that can, or must, be associated with each instance of another entity.
*Minimum* cardinality
The minimum number of instances of one entity that may be associated with each instance of another entity.
*MAXIMUM* cardinality
The maximum number of instances of one entity that may be associated with each instance of another entity.
A database is an organized collection of ________ related data.

A) logically.
B) physically.
C) loosely.
D) badly.

A) logically
Data processed in a way that increases a user’s knowledge is:

A) text.
B) graphics.
C) information.
D) hyperlink.

C) information
Data that describe the properties of other data are:

A) relationships.
B) logical.
C) physical.
D) none of the above.

D) none of the above.
One disadvantage of file processing systems is:

A) reduced data duplication.
B) program-data independence.
C) limited data sharing.
D) enforcement of integrity constraints.

C) limited data sharing.
Program-data dependence is caused by:

A) file descriptors being stored in each application.
B) data descriptions being stored on a server.
C) data descriptions being written into programming code.
D) data cohabiting with programs.

A) file descriptors being stored in each application.
Because applications are often developed independently in file processing systems:

A) the data is always non-redundant.
B) unplanned duplicate data files are the rule rather than the exception.
C) data can always be shared with others.
D) there is a large volume of file I/O.

B) unplanned duplicate data files are the rule rather than the exception.
All of the following are primary purposes of a database management system (DBMS) EXCEPT:

A) creating data.
B) updating data.
C) storing data.
D) providing an integrated development environment.

D) providing an integrated development environment.
Which of the following is NOT an advantage of database systems?

A) Redundant data.
B) Program-data independence.
C) Better data quality.
D) Reduced program maintenance.

A) Redundant data
Databases may be more expensive to maintain than files because of:

A) the need for specialized personnel.
B) the complexity of the database environment.
C) backup and recovery needs.
D) all of the above.

D) all of the above.
Which of the following is NOT a cost and/or risk of the database approach?

A) Specialized personnel.
B) Cost of conversion.
C) Improved responsiveness.
D) Organizational conflict.

C) Improved responsiveness
The logical representation of an organization’s data is called a(n):

A) database model.
B) entity-relationship model.
C) relationship systems design.
D) database entity diagram.

B) entity-relationship model.
In an E-R diagram, there are ________ business rule(s) for every relationship.

A) two.
B) three.
C) one.
D) none.

A) two
Business policies and rules govern all of the following EXCEPT:

A) managing employees.
B) creating data.
C) updating data.
D) removing data.

A) managing employees.
Which of the following is NOT a good characteristic of a data name?

A) Relates to business characteristics.
B) Readable.
C) Repeatable.
D) Relates to a technical characteristic of the system.

D) Relates to a technical characteristic of the system
Customers, cars, and parts are examples of:

A) entities.
B) attributes.
C) cardinals.
D) relationships.

A) entities.
A person’s name, birthday, and social security number are all examples of:
A) attributes.
B) entities.
C) relationships.
D) descriptors.
A) attributes.
Which of the following criteria should be considered when selecting an identifier?

A) Choose an identifier that is stable.
B) Choose an identifier that will not be null.
C) Choose an identifier that doesn’t have large composite attributes.
D) All of the above.

An entity that associates the instances of one or more entity types and contains attributes specific to the relationships is called a(n):

A) associative entity.
B) connecting entity.
C) intersectional entity.
D) all of the above.

A) associative entity.
The number of entity types that participate in a relationship is called the:
A) number.
B) identifying characteristic.
C) degree.
D) counter.
C) degree.
A relationship between the instances of a single entity type is called a(n) ________ relationship.
A) ternary.
B) primary.
C) binary.
D) unary.
D) unary
Physical database design decisions must be made carefully because of impacts on:
A) data accessibility.
B) response times.
C) security.
D) all of the above.
D) all of the above.
An attribute (or attributes) that uniquely identifies each row in a relation is called a:

A) column.
B) foreign field.
C) primary key.
D) duplicate key.

C) primary key.
An attribute in a relation of a database that serves as the primary key of another relation in the same database is called a:

A) link attribute.
B) link key.
C) foreign key.
D) foreign attribute.

C) foreign key.
A primary key that consists of more than one attribute is called a:
A) foreign key.
B) composite key.
C) multivalued key.
D) cardinal key.
B) composite key.
Which of the following are properties of relations?
A) Each attribute has a unique name.
B) No two rows in a relation are identical.
C) There are no multivalued attributes in a relation.
D) All of the above.
D) All of the above.
The ________ states that no primary key attribute may be null.

A) referential integrity constraint.
B) entity integrity rule.
C) partial specialization rule.
D) range domain rule.

B) entity integrity rule
A rule that states that each foreign key value must match a primary key value in the other relation is called the:

A) referential integrity constraint.
B) key match rule.
C) entity key group rule.
D) foreign/primary match rule.

A) referential integrity constraint.
8) Which of the following are anomalies that can be caused by redundancies in tables?

A) Insertion.
B) Deletion.
C) Modification.
D) All of the above.

D) All of the above
A relation that contains minimal redundancy and allows easy use is considered to be:

A) clean.
B) simple.
C) complex.
D) well-structured.

D) well-structured.
Schema
Listing the table (ENTITY) and its Attributes in text form.

Example:

CUSTOMER: customer I.d., first_name, last_name, credit

SALES_ORDER: order#, date

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