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Tutorial Questions

Question 2.1

In the beginning, file system was used to handle the database. In this system each application

defines and defined and maintained its own data and thus data was not independent of these

applications.

But now database management systems (DBMS) are used to manage the databases. These systems

keeps the data independent of applications and each application can access the data through the

same interface of database management systems. Application programs are immune to changes in

logical or physical organization of data and vice versa. Data can be defined at two levels, either

logically or physically.

Logical data independence refers to the immunity of application programs to the logical structureof database. For example if we add more attributes to a relation in database, the data access

methods used by application should not be affected.

Physical dataindependence says that the application programs should not be concerned with the

physical data organization. Therefore the application programs should not need to be modified

when physical data organization is changed.

Question 2.2

ExternalThe users view of the database. This level describes that part of the database that is

relevant to each user.

Conceptual The community view of the database. This level describes what data is stored in the

database and the relationships among the data.

Internal The physical representation of the database on the computer. This level describes how the

data is stored in the database.

Question 2.5

Types of facility that would be expected to be provided in a multi user DBMS are:

Data storage, retrieval, and update A user accessible catalog Transaction support ensure either that all the updates corresponding to a given

transaction are made or that none of them is made.

Concurrency control services ensure that the database is update correctly when multipleusers are updating the database concurrently.

Recovery services recovering the database in the event that the database is damaged. Authorisation services ensure that only authorised users can access the database. Support for data communication capable of integrating with communication software.

Integrity services ensure that both the data in the database and changes to the data followcertain rules.

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Services to promote data independence Utility services

Question 2.6

I think that the following facilities arent needed on a PC DBMS:

Concurrency control servicesyou dont need multiple users updating the database on astandalone PC. Dont think there is a need to share.

Authorisation serviceson a standalone PC, I dont think there is need for the security onthe database except for profile security.

Services to promote data independenceQuestion 3.1

Client-server architecture refers to the way in which software components react. There is a client

process that requires some resource, and the server that provides the resource. Client-server

architecture is different to a web service as it is a software system designed to support interoperable

machine-to-machine interaction over a network. Another comparison is a DDBMS (Distributed

DBMS) that is the software system that permits the management of the distributed database and

makes the distribution transparent to users.

List 6 attributes, data types and common values for a motor vehicle e.g.

Attribute Data type Maximum

Size/dimension

Common values

1. Vehicle make Text 20 Toyota, Holden

2. Vehicle model Text 20 Corolla, Nivara

3. Year Number 40 1994, 2004

4. Kilometres Number 20 78,000

5. Transmission Text 20 Automatic, Manual

6. Colour Text 20 Black, White

Which one of these attributes would uniquely identify every instance of a motor

vehicle? A unique identifying attribute (or combination of attributes) is a key. If you

don't have a key amongst your chosen attributes add an extra attribute which can be

used as a key.

We would have to insert a vehicle ID attribute as a unique identifier.