Week 2 Flashcards

1
Q

ANSI-SPARC Three-Level Architecture

A

External
Conceptual
Internal

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2
Q

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

A

External level

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3
Q

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

A

Conceptual level

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4
Q

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

A

Internal level

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5
Q

Objectives of Three-Level Architecture

A

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.

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6
Q

Data Independence and the ANSI-SPARC Three-Level Architecture

A

External/Conceptual mapping = Logical data independence

Conceptual/Internal mapping = Physical data independence

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7
Q

Logical Data Independence

A

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.

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8
Q

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.

A

Physical Data Independence

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9
Q

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.

A

Logical Data Independence

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10
Q

Database Languages

A

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

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11
Q

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

plus any associated integrity and security constraints.

A

Data Definition Language (DDL)

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12
Q

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

A

Data Manipulation Language (DML)

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13
Q

allows user to tell system exactly how to manipulate data.

A

Procedural DML

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14
Q

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

A

Non-Procedural DML

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15
Q

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

A

Data Model

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16
Q

Data Model comprises:

A

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

17
Q

purpose of data model

A

To represent data in an understandable way.

18
Q

Categories of data models include:

A

Object-based
Record-based
Physical.

19
Q

Object-Based Data Models includes

A

Entity-Relationship
Semantic
Functional
Object-Oriented.

20
Q

Record-Based Data Models includes

A

Relational Data Model
Network Data Model
Hierarchical Data Model.

21
Q

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

A

Conceptual schema

22
Q

______ 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.

A

Conceptual modeling

23
Q

____ is a conceptual data model.

A

Result

24
Q

Functions of a DBMS

A

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.

25
Q

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.

A

system catalog

26
Q

one of the fundamental components of DBMS

A

system catalog

27
Q

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.

A

system catalog

28
Q

Multi-User DBMS Architectures

A

Teleprocessing

File-server

Client-server

29
Q

Traditional architecture.

Single mainframe with a number of terminals attached.

Trend is now towards downsizing.

A

Teleprocessing

30
Q

______ is connected to several workstations across a network.

Database resides on ____.

DBMS and applications run on each workstation.

A

file-server

31
Q

Disadvantages of file-server include:

A

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

32
Q

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

A

Traditional Two-Tier Client-Server

33
Q

Advantages of traditional two-tier client-server include:

A

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

34
Q

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.

A

Three-tier Client-Server

35
Q

Advantages of three-tier client-server include:

A

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.