ANSI/SPARC

Question 1

what does ANSI/SPARC stand for ?

Answer 1

American National Standard Institute - standards planning and requirements committee

Question 2

what are the 3 levels of the ANSI/SPARC database system ?

Answer 2

1. view layer / external
2. logical layer / conceptual
3. physical layer/ internal

Question 3

describe the physical layer ?

Answer 3

physical layer discribes how data is actually stored in a database. The Physical layer is above the database in the architectural diagram

Question 4

what is the conceptual/ logical level?

Answer 4

this level describes how the database will view to the user conceptually and the relationship between various data tables.
the reason for the database such as ; relationship among data , schema of data etc , is stored in this level

• the conceptual level does not care about how the data is actually stored

Question 5

what is the level/schema above the internal schema

Answer 5

the view / external level

Question 6

the _____ only shows the relevant data base content to the user in the form of views and hides the rest of the data

Answer 6

View Level

Question 7

what is the other name for physical layer

Answer 7

internal layer

Question 8

How are records described in the Physical layer ?

Answer 8

records can be described as blocks of storage ( gigabytes TB etc)

*the details are hidden from the programmer

Question 9

how are records described in the logical level?

Answer 9

records can be described as fields and attributes along with their data types and relationships

Question 10

what level do programmers generally work

Answer 10

logical / conceptual level

Question 11

At what level do users interact with the database system ?

Answer 11

View level/ external level

Question 12

How do users handle data when accessing the system ?

Answer 12

users are not aware of how or what data is stored

Question 13

the process of hiding complex and irrelevant details from the user is referred to as

Answer 13

Data abstraction

Question 14

What is mapping ?

Answer 14

This is the process of transferring results and requests among the three levels

Question 15

What is data Independence ?

Answer 15

this is the ability to modify a schema in one level without affecting the schema in the next higher level

Question 16

what are the two types of data independency in the database system?

Answer 16

1. physical independency - the ability to modify the physical schema without requiring any change the logical schema and application programs
2. logical independency - the ability to modify the logical layer without requiring any change in the application program ( view Layer / external layer )

Question 17

in what scenario would you want to modify the physical layer ?

Answer 17

in a situation where you would want to improve performance of a database

Question 18

why would you modify the logical layer ?

Answer 18

this is only neccessary when the logical structure of the database is changed