Week 2

Question 1

ANSI-SPARC Three-Level Architecture

Answer 1

External
Conceptual
Internal

Question 2

Users’ view of the database.
Describes that part of database that is relevant to a particular user.

Answer 2

External level

Question 3

Community view of the database.
Describes what data is stored in database and relationships among the data.

Answer 3

Conceptual level

Question 4

Community view of the database.
Describes what data is stored in database and relationships among the data.

Answer 4

Internal level

Question 5

Objectives of Three-Level Architecture

Answer 5

All users should be able to access same data.

A user’s view is immune to changes made in other views.

Users should not need to know physical database storage details.

DBA should be able to change database storage structures without affecting the users’ views.

Internal structure of database should be unaffected by changes to physical aspects of storage.

DBA should be able to change conceptual structure of database without affecting all users.

Question 6

Data Independence and the ANSI-SPARC Three-Level Architecture

Answer 6

External/Conceptual mapping = Logical data independence

Conceptual/Internal mapping = Physical data independence

Question 7

Logical Data Independence

Answer 7

Refers to immunity of external schemas to changes in conceptual schema.
Conceptual schema changes (e.g. addition/removal of entities).
Should not require changes to external schema or rewrites of application programs.

Question 8

Refers to immunity of conceptual schema to changes in the internal schema.
Internal schema changes (e.g. using different file organizations, storage structures/devices).
Should not require change to conceptual or external schemas.

Answer 8

Physical Data Independence

Question 9

Refers to immunity of external schemas to changes in conceptual schema.
Conceptual schema changes (e.g. addition/removal of entities).
Should not require changes to external schema or rewrites of application programs.

Answer 9

Logical Data Independence

Question 10

Database Languages

Answer 10

Data Definition Language (DDL)
Data Manipulation Language (DML)
Procedural DML
Non-Procedural DML
Fourth Generation Languages

Question 11

Allows the DBA or user to describe and name entities, attributes, and relationships required for the application

plus any associated integrity and security constraints.

Answer 11

Data Definition Language (DDL)

Question 12

Provides basic data manipulation operations on data held in the database.

Answer 12

Data Manipulation Language (DML)

Question 13

allows user to tell system exactly how to manipulate data.

Answer 13

Procedural DML

Question 14

allows user to state what data is needed rather than how it is to be retrieved.

Answer 14

Non-Procedural DML

Question 15

Integrated collection of concepts for describing data, relationships between data, and constraints on the data in an organization.

Answer 15

Data Model

Question 16

Data Model comprises:

Answer 16

a structural part;
a manipulative part;
possibly a set of integrity rules.

Question 17

purpose of data model

Answer 17

To represent data in an understandable way.

Question 18

Categories of data models include:

Answer 18

Object-based
Record-based
Physical.

Question 19

Object-Based Data Models includes

Answer 19

Entity-Relationship
Semantic
Functional
Object-Oriented.

Question 20

Record-Based Data Models includes

Answer 20

Relational Data Model
Network Data Model
Hierarchical Data Model.

Question 21

_____ is the core of a system supporting all user views.

Answer 21

Conceptual schema

Question 22

______ is process of developing a model of information use that is independent of implementation details.

Should be complete and accurate representation of an organization’s data requirements.

Answer 22

Conceptual modeling

Question 23

____ is a conceptual data model.

Answer 23

Result

Question 24

Functions of a DBMS

Answer 24

Data Storage, Retrieval, and Update.

A User-Accessible Catalog.

Transaction Support.

Concurrency Control Services.

Recovery Services.

Authorization Services.

Support for Data Communication.

Integrity Services.

Services to Promote Data Independence.

Utility Services.

Question 25

Repository of information (metadata) describing the data in the database.
One of the fundamental components of DBMS.
Typically stores:
names, types, and sizes of data items;
constraints on the data;
names of authorized users;
data items accessible by a user and the type of access;
usage statistics.

Answer 25

system catalog

Question 26

one of the fundamental components of DBMS

Answer 26

system catalog

Question 27

Typically stores:
names, types, and sizes of data items;
constraints on the data;
names of authorized users;
data items accessible by a user and the type of access;
usage statistics.

Answer 27

system catalog

Question 28

Multi-User DBMS Architectures

Answer 28

Teleprocessing

File-server

Client-server

Question 29

Traditional architecture.

Single mainframe with a number of terminals attached.

Trend is now towards downsizing.

Answer 29

Teleprocessing

Question 30

______ is connected to several workstations across a network.

Database resides on ____.

DBMS and applications run on each workstation.

Answer 30

file-server

Question 31

Disadvantages of file-server include:

Answer 31

Significant network traffic.
Copy of DBMS on each workstation.
Concurrency, recovery and integrity control more complex.

Question 32

Client (tier 1) manages user interface and runs applications.
Server (tier 2) holds database and DBMS.

Answer 32

Traditional Two-Tier Client-Server

Question 33

Advantages of traditional two-tier client-server include:

Answer 33

wider access to existing databases;
increased performance;
possible reduction in hardware costs;
reduction in communication costs;
increased consistency.

Question 34

Client side presented two problems preventing true scalability:
‘Fat’ client, requiring considerable resources on client’s computer to run effectively.
Significant client side administration overhead.

By 1995, three layers proposed, each potentially running on a different platform.

Answer 34

Three-tier Client-Server

Question 35

Advantages of three-tier client-server include:

Answer 35

Advantages:
‘Thin’ client, requiring less expensive hardware.
Application maintenance centralized.
Easier to modify or replace one tier without affecting others.
Separating business logic from database functions makes it easier to implement load balancing.
Maps quite naturally to Web environment.