Lesson 2.3: Levels of Database Architecture

Question 1

ANSI Standards Planning and Requirements Committee (SPARC) architecture is divided into three levels

Answer 1

External Level
Conceptual Level
Internal Level

Question 2

user’s view of the database

Answer 2

External Level

Question 3

the community view of the database

Answer 3

Conceptual Level

Question 4

physical representation of the database on the computer

Answer 4

Internal Level

Question 5

part of the database that is relevant to the user and is concerned with the way the data is seen by individual users

Answer 5

External Level

Question 6

describes what data is stored in the database and the relationships among the data

Answer 6

Conceptual Level

Question 7

describes how the data is stored in the database and is concerned with the way the data is physically stored

Answer 7

Internal Level

Question 8

conceptual level represents

Answer 8

• all entities, their attributes and their relationships
• constraints on the data
• semantic information about the data
• security and integrity information

Question 9

internal level represents

Answer 9

• storage space allocation for data and indexes
• record descriptions for storage (with stored sizes for data items)
• record placement
• data compression and data encryption techniques

Question 10

reasons of separation

Answer 10

• Each user should be able to access the same data, but may have different view of the data.
• User should not have to deal directly with physical data storage detail.
• The DBA should be able to change the database storage structure w/o affecting the users’ view
• The internal structure of the database should be unaffected by changes to the physical aspects of storage.

Question 11

an individual user level

Answer 11

external level

Question 12

in external level, all such languages will include a ___

Answer 12

data sublanguage (DSL)

Question 13

subset of the total language that is concerned specifically with database objects nad operations, embedded within the corresponding host language and is responsible for providing various nondatabase facilities

Answer 13

data sublanguage (DSL)

Question 14

what particular DSL is supported?

Answer 14

SQL

Question 15

A DSL is a combination of at least two subordinate languages

Answer 15

• Data Definition Language (DDL)
  
  • supports the definition or declaration of database objects
• Data Manipulation Language (DML)
  
  • supports the manipulation or processing of such objects

Question 16

content of the database as seen by some particular user that consists of many occurrences of each of many types of external record

Answer 16

external view

Question 17

written using the DDL portion of the user’s DSL.

Answer 17

external schema

Question 18

a representation of the entire information content of the database in a form that is somewhat abstract in comparison with the way in which the data is physically stored and is a view of the total database content that consists of many occurrences of each of many types of conceptual record

Answer 18

Conceptual view / conceptual level?

Question 19

The conceptual view is defined by means of the ___

Answer 19

conceptual schema

Question 20

includes definitions of each of the various conceptual record types

Answer 20

conceptual schema

Question 21

written using another DDL, the conceptual DDL

Answer 21

conceptual schema

Question 22

a schema intended to include the a great many additional features, such as security and integrity constraints

Answer 22

conceptual schema

Question 23

t/f A conceptual record is not necessarily the same as either an external record or a stored record.

Answer 23

true

Question 24

low-level representation of the entire database

Answer 24

internal level

Question 25

consists of many occurrences of each of may types of internal record

Answer 25

internal level

Question 26

internal view is still at one remove from the physical level since it does not deal in terms of physical records, also called _____ or pages - nor with any device specific considerations such as cylinder or track sizes.

Answer 26

blocks

Question 27

described by means of the internal schema, which not only defines the various stored record types but also specifies what indexes exist, how stored fields are represented, what physical sequence the stored records are in and so on.

Answer 27

internal view

Question 28

the database system architecture involves certain mappings

Answer 28

The conceptual/internal mapping | The conceptual/external mapping

Question 29

defines the correspondence between the conceptual view and the stored database It specifies how conceptual records and fields are represented at the internal level If the structure of the stored database is changed - that is if a change is made to the storage structure definition - then the conceptual/internal mapping must be changed accordingly, so that the conceptual schema can remain invariant.

Answer 29

The conceptual/internal mapping

Question 30

- defines the correspondence between a particular **external view and the conceptual view** - In general, the differences that can exist between these two levels are analogous to those that can exist between the conceptual view and the stored database.

Answer 30

The conceptual/external mapping

Question 31

A system provides ____________- if users and user programs are immune to changes in the physical structure of the stored database.

Answer 31

physical data independence

Question 32

Analogously, a system provides ________________ if users and user programs are also immune to changes in the logical structure of the database.

Answer 32

logical data independence