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DBMS > DBMS Chapter 2 > Flashcards

DBMS Chapter 2 Flashcards

1
Q

Data abstraction

A

The suppression of details and highlighting of the essential features

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2
Q

Data Model

A

A set of concepts to describe the structure of a database, and certain constraints that the database should obey.

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3
Q

Client Module

A

Designed so that it will run on a user workstation or PC

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4
Q

Server Module

A

Handles data storage, access, search functions

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5
Q

Categories of data models

A

Conceptual (high-level, semantic) data models:
Physical (low-level, internal) data models:
Implementation (representational) data models:

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6
Q

Conceptual (high-level, semantic) data models

A

Provide concepts that are close to the way many users perceive data.

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7
Q

Physical (low-level, internal) data models

A

Provide concepts that describe details of how data is stored in the computer

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8
Q

Implementation (representational) data models

A

Provide concepts that fall between the above two, balancing user views with some computer storage details.

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9
Q

Advantage of Hierarchical Model

A
  • Hierarchical Model is simple to construct and operate on
  • Corresponds to a number of natural hierarchically organized domains
  • Language is simple
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10
Q

Disadvantage of Hierarchical Model

A
  • Navigational and procedural nature of processing
  • Database is visualized as a linear arrangement of records
  • Little scope for “query optimization”
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11
Q

Advantages of Network Model

A
  • Network Model is able to model complex relationships.

- Can handle most situations for modeling using record types and relationship types.

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12
Q

Disadvantage of Network Model

A

Navigational and procedural nature of processing

Database contains a complex array of pointers that thread through a set of records.

Little scope for automated “query optimization”

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13
Q

Database Schema

A

The description of a database. Includes descriptions of the database structure and the constraints that should hold on the database.

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14
Q

Schema Diagram

A

A diagrammatic display of (some aspects of) a database schema.

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15
Q

Schema Construct

A

A component of the schema or an object within the schema

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16
Q

Database Instance

A

The actual data stored in a database at a particular moment in time

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17
Q

Database State

A

Refers to the content of a database at a moment in time.

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18
Q

Valid State

A

A state that satisfies the structure and constraints of the database.

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19
Q

Database schema vs. Database state

A
  • The database schema changes very infrequently. The database state changes every time it’s updated
  • Schema is also called intension, whereas state is called extension.
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20
Q

3-schema Architecture

A

Internal schema, Conceptual schema, External schema

21
Q

Internal schema

A

Describes physical storage structures and access paths. Typically uses a physical data model.

22
Q

Conceptual schema

A

Describes the structure and constraints for the whole database for a community of users. Uses a conceptual or an implementation data model.

23
Q

External schema

A

Describes the various user views. Usually uses the same data model as the conceptual level.

24
Q

Mappings

A

Processes of transforming requests and results between levels

25
Q

Data independence

A

defined as the capacity to change the schema at one level of a database system without having to change the schema at the next higher level

26
Q

Logical Data Independence

A

Can change the conceptual schema without changing the external schemas

27
Q

Physical Data Independence

A

Can change the internal schema without changing the conceptual schema

28
Q

Data Definition Language (DDL)

A

Used by the DBA and database designers to specify the conceptual schema of a database.

29
Q

Storage definition language (SDL)

A

Used to specify the internal schema

30
Q

View definition language (VDL)

A

used to specify user views and their mappings to the concept schema, used to define conceptual and external schemas

31
Q

Data Manipulation Language (DML):

A

Used to specify database retrievals and updates.

32
Q

2-types of DMLS

A

(high level)Non-procedural Languages and (low level)procedural languages

33
Q

High Level language

A

Set-oriented and specify what data to retrieve than how to retrieve

34
Q

Low Level language

A

Record-at-a-time; they specify how to retrieve data and include constructs such as looping.

35
Q

DBMS Interfaces

A

Stand-alone query language interfaces

Programmer interfaces for embedding DML in programming languages

36
Q

Database System Utilities Functions

A
  • Loading data
  • Backing up database
  • Reorganizing file structures.
  • Report generation
  • Performance monitoring
37
Q

Data dictionary

A

Used to store schema descriptions as well as design decisions, application program descriptions, user information, usage standards, etc.

38
Q

Backup

A

Backup of database by dumping into different file organizations

39
Q

Application development environment

A

Systems provide an environment for developer database applications and including database design

40
Q

Centralized DBMS

A

Combines everything into single system

- DBMS software, hardware, application programs and user interface

41
Q

Client

A

User machine that provide appropriate interfaces and a client-version of the system to access and utilize the server resources.

42
Q

Server

A

System containing both hardware and software that can provide services to the client machines

43
Q

DBMS Server

A

Provides database query and transaction services to the clients

44
Q

Two Tier Client-Server Architecture

A

User Interface Programs and Application Programs run on the client side
client—>Communication network —>Server
- Simplicity and seamless compatibility

45
Q

Advantage of Two Tier Client-Server Architecture

A

The advantages of this architecture are its simplicity and seamless compatibility with existing
systems.

46
Q

Three Tier Client-Server

A

Adds a web server between the client and database server

Client - Better security

47
Q

web server(middle tier)

A

This server plays an intermediary role by running application programs and storing business rules (procedures or constraints) that are used to access data from the database server.

48
Q

Variations of Distributed Environments

A

Homogeneous DDBMS
Heterogeneous DDBMS
Federated or Multidatabase Systems

49
Q

Classification of DBMSs

A

Traditional:Relational, Network, Hierarchical.
Emerging: Object-oriented, Object-relational

DBMS (8 decks)

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