Data Models: Lesson 2

Question 1

Why is data models important?

Answer 1

To facilitate interaction between the designer, applications programmer and the end user.
Data models organizes data for various users

Question 2

What are the 4 data model basic building blocks?

Answer 2

entity, attribute, relationship and constraints

Question 3

What is a entity?

Answer 3

It is anything about which data are to be collected and stored

Question 4

What is a attribute?

Answer 4

It is a characteristic of a entity

Question 5

What is a constraint?

Answer 5

It is a restriction placed on the data

Question 6

What are the sources of business rules?

Answer 6

Company manager, department manager, policy maker, written documentation and direct interaction with the end user.

Question 7

What are the 3 types of written documentation in business rules?

Answer 7

Standards, procedures and operations manuals

Question 8

Documenting and identifying business rules is important because?

Answer 8

Standardize the companys view on data
Constitutes a communication tool between the designer and the end user
Allows designer to understand the scope, role and nature of the data
Allows the designer to understand the businesses processes
Promote the creation of an accurate data model

Question 9

What are the 5 different types of data models?

Answer 9

Hierarchical, Network, Relational, Entity relationship and object oriented

Question 10

Why was the hierarchical model developed and what does it look like?

Answer 10

To manage large amounts of data for complex manufacturing projects and it looks like an upside down tree

Question 11

What are the advantages of the hierarchical model?

Answer 11

Many of the hierarchical data model’s features formed the foundation for current data models
Its database application advantages are replicated, albeit in a different form, in current database environments

Question 12

What are the disadvantages of the hierarchical model?

Answer 12

Complex to implement
difficult to manage
lacks structural independence
lack of standards

Question 13

Why was the network model created?

Answer 13

To impose the standard for data bases
to improve database performance
it represents complex data relationships more effectively

Question 14

What doe CODASYL stand for?

Answer 14

Conference on Data Systems languages

Question 15

What does DBTG stand for?

Answer 15

Database Task Group

Question 16

What is a schema in the network model?

Answer 16

It is a conceptual organization of the entire database as viewed by the database administrator

Question 17

What does DML stand for and what does it do?

Answer 17

Data Management Language, it is used to define the environment where the data can be managed

Question 18

What does DDL stand for and what does it do in the schema DDL?

Answer 18

Data Definition Language, it enables the database administrator to define schema components

Question 19

What does subschema DDL so?

Answer 19

It allows the program application to define the database components that will be used

Question 20

What are the 2 record types in the network model?

Answer 20

Owner and member

Question 21

What are the disadvantages of the network model?

Answer 21

Too cumbersome
The lack of ad hoc query capability put heavy pressure on programmers
Any structural change in the database could produce havoc in all application programs that drew data from the database
Many database old-timers can recall the interminable information delays

Question 22

What does RDBMS stand for?

Answer 22

Relational Database Management System

Question 23

What is the most important function of the relational model?

Answer 23

It can hide the complexities of the relational model from the user

Question 24

What does SQL stand for and what does it do?

Answer 24

Structured Query Language, it allows the user to specify what must be done without specifying how to do it

Question 25

SQL-based relational database application involves what 3 things

Answer 25

User interface
a set of tables in the database
SQL engine

Question 26

What does UML stand for and what is its use?

Answer 26

Unified modeling language, it is used to produce entity relationship models

Question 27

What does ERD stand for?

Answer 27

Entity Relationship Diagram

Question 28

What is the entity instances other word and what is it?

Answer 28

Entity occurrence, it is a row in a table

Question 29

What is a entity set?

Answer 29

It is a collection of like entities

Question 30

What does OODM stand for and it is a basis for what?

Answer 30

Object oriented data model, it is the basis for the object oriented database management system (OODBMS)

Question 31

What is inheritance?

Answer 31

It is the ability of an object within the class hierarchy to inherit the attributes and methods of the classes above

Question 32

What does ERDM stand for?

Answer 32

Extended Relational Data model

Question 33

What is the primary focus of the ERDM model?

Answer 33

It is primarily geared to business applications

Question 34

What is data abstraction?

Answer 34

It is the way of classifying data models

Question 35

What does ANSI and SPARC stand for and what did they do?

Answer 35

American National Standards institution, Standards Planning and Requirements Committee
They defined a framework for data modeling on degrees of data abstraction

Question 36

What are the 3 data abstractions?

Answer 36

External
Conceptual
Internal

Question 37

What is the external model?

Answer 37

It is the end users view of the data environment

Question 38

What is the conceptual model?

Answer 38

Represents the global view of the entire database

Question 39

What is the internal model?

Answer 39

Representation of the database as “seen” by the DBMS

Question 40

What is the physical model?

Answer 40

Operates at lowest level of abstraction, describing the way data are saved on storage media such as disks or tapes