1. TOPIC 1 INTRODUCTION TO DATABASE TECHNOLOGY Dr. WENNY RAHAYU
Readings : Chpts 1 & 2 Elmasri & Navathe

2. How would you manage this information? Get a good book­keeper!
Why use a DATABASE?
Imagine owning a business, say a video rental agency, what sort of information, that is data, would you have to keep?
Current stock: titles, manufacturers
Customer details
Current loans, past loans, hold requests (who by?, what of?)
Staff details
Suppliers: videos, snacks
Accounts, income, outgoings, overdue fines
How would you manage this information? Get a good book­keeper!
The book­keeper will create a database for you.
Topic 1 : Introduction to Database Technology

3. What questions might you ask the book­keeper?
Why use a DATABASE?
So, you've got a database
What questions might you ask the book­keeper?
How many videos are overdue?
Do we have enough copies of Harry Potter?
Can we pay the staff this week?
Which customers haven't been in for a while? We should send them this special offer.
These questions can be translated into queries, that is, written in a form a database system can understand.
Topic 1 : Introduction to Database Technology

4. Good use of your database
Why use a DATABASE?
Good use of your database
You and the book­keeper need to be able to discuss the information stored about your business.
Information can be described by a model, which (as for queries) should be written in a language the database understands.
The stored information should be correct and sensible.
Topic 1 : Introduction to Database Technology

5. Why use a DATABASE? Database uses: Retail information.
Hospital records: treatments available, per­patient information, per­doctor information, ward and bed availability, billing data.
Mass storage:
Weather records: thousands of sites, many observations per day, many values per observation, many years of records.
Satellite images.
Telephone records: who to, who from, what route, how long, what costing?
Databases provide a uniform framework for handling these very different activities.
Topic 1 : Introduction to Database Technology

6. “ A shared collection of related data
What is a DATABASE?
“ A shared collection of related data
designed to meet the information needs
of an organisation.”
Topic 1 : Introduction to Database Technology

7. Database vs. Database System
A Database is:
A representation of some aspect of the real world; or perhaps, a collection of data elements (facts) representing real­world information.
Logically coherent and internally consistent.
Designed, built, and populated with data for a specific purpose.
A Database System is:
A software system for managing databases: definition and creation, population, querying.
These terms are used somewhat interchangeably - don't get confused.
Topic 1 : Introduction to Database Technology

8. A File System Personnel Dept. Accounting Dept. Sales Dept. Employees
Accounts
Inventory
Customers
Sales
Topic 1 : Introduction to Database Technology

9. A Database System DBMS Personnel Dept. Sales Dept. Accounting Dept.
Employees
Customers
Sales
Inventory
Accounts
Personnel Dept.
DBMS
Sales Dept.
Accounting Dept.
Topic 1 : Introduction to Database Technology

10. An Example of a Database
STUDENT
UNIT
Topic 1 : Introduction to Database Technology

11. An Example of a Database
STUDENT_RESULT
PRE_REQUISITE
Topic 1 : Introduction to Database Technology

12. Predictions & Challenges for Database Systems in the New Millennium (based on P. Selinger, IBM Almaden Research Centre, VLDB)
Database Systems = Telephone
Ease of Use
Connect to anything across the world
Recognised standards
Universal
Industrial strength
Growing functionality

13. a) Database Administrators ( DBA )
Database Users
a) Database Administrators ( DBA )
The Database Administrator is responsible for authorizing access to the database, for coordinating and monitoring its use, and for acquiring software and hardware resources as needed.
b) Database Designers
Database Designers are responsible for identifying the data stored in the database and for choosing appropriate structures to represent and store this data.
Topic 1 : Introduction to Database Technology

14. d) System Analysts and Application Programmers
Database Users
c) End Users
Casual end users
Naive users
Sophisticated end users
d) System Analysts and Application Programmers
System analysts determine the requirements of end users, and develop specifications for canned transactions that meet these requirements. Application programmers implement these specifications as programs; then they test, debug, document, and maintain these canned transactions.
Topic 1 : Introduction to Database Technology

15. e) DBMS Designers and Implementers
Database Users
e) DBMS Designers and Implementers
DBMS Designers and Implementers are responsible for designing and implementing the DBMS modules and interfaces as a software package.
f) Tool Developers
Tools are software packages that facilitate database system design and use, and help in improving performance. Tool Developers include persons who design and implement such tools. In many cases, independent software vendors develop and market these tools.
g) Operators and Maintenance Personnel
These are the system administration personnel who are responsible for the actual running and maintenance of the hardware and software environment for the database system.
Topic 1 : Introduction to Database Technology

16. Characteristics of a Database Approach
a) Self-describing
A DBMS catalog stores the description of the database. The description is called meta-data. This allows the DBMS software to work with different databases.
b) Data Independence
The system data descriptions are separated from the application programs. Any changes to the data structures can be kept isolated from the rest of the application program. This is because the data structures are managed by the DBMS and not embedded in a program such as they are with the processing system (E.g. A C++ record structure)
Topic 1 : Introduction to Database Technology

17. Characteristics of a Database Approach
c) Multiple Views of Data
A view may be a subset of the database or it may contain virtual data that is derived from the database files but is not explicitly stored. Some users may not need to be aware of whether the data they refer to is stored or derived
d) Data Sharing
The integration of all the data in an organisation provides the ability to produce more information from that data.
Topic 1 : Introduction to Database Technology

18. Characteristics of a Database Approach
e) Transaction Processing
The Database System must include concurrency control software to ensure that several users trying to update the same data do so in a controlled manner so that the result of the updates is correct. These are generally called transaction processing applications.
Topic 1 : Introduction to Database Technology

19. Benefits of a Database Approach
a) To Control Data Redundancy
Data redundancy leads to three major problems :
Duplicate effort
Waste of storage
Inconsistency of data
However, please note that in Relational systems redundancy will still exist as some fields need to be duplicated to provide relationships, but such redundancy is controlled and kept to a minimum.
Topic 1 : Introduction to Database Technology

20. Benefits of a Database Approach
Example
(1) Data Redundancy : Duplicate Effort and Waste of Storage
STUDENT_GRADE
(2) Data Redundancy Leads to Inconsistencies
STUDENT_GRADE
Topic 1 : Introduction to Database Technology

21. Benefits of a Database Approach
b) Data Integrity
Controlled redundancy leads to reliable and consistent data
c) Data Constraints
Most databases applications have certain Integrity constraints that must hold for the data. A DBMS should provide capabilities for defining and enforcing these constraints. The simplest type of integrity constraint involves specifying a data type for each data item.
Topic 1 : Introduction to Database Technology

22. The Benefit of Database Approach
d) Restricting Unauthorised Accesss
A DBMS should provide a security and authorisation subsystem, which the DBA uses to create accounts and to specify account restrictions. The DBMS should then enforces these restrictions automatically.
e) Programming Advantages
Persistent storage for program
Objects and Data Structure
Multiple user interface.
f) Providing Backup and Recovery
If the computer system fails in the middle of a complex update program, the recovery subsystem is responsible for making sure that the database is restored to the state it was in before the program started executing.
Topic 1 : Introduction to Database Technology

23. Summary Benefits of a Database Approach
Need to control redundancy - don't want multiple versions of the same data
Need to control consistency and coherency - the data should make sense
Need to control access, that is, who gets to use or change the data
Need for persistent, reliable storage
Accessed in multiple ways
Need to understand the complex relationships between the different kinds of stored data items.
Topic 1 : Introduction to Database Technology

24. DBMS Architecture
In order to achieve the characteristics and benefits of a database approach as listed in the above sections, an architecture for a database system called ANSI/SPARC architecture or Three-Schema architecture was proposed.
Topic 1 : Introduction to Database Technology

25. ….. ….. DBMS Architecture : Three Schema Architecture
END USERS
EXTERNAL
VIEW1
VIEWn
EXTERNAL LEVEL
…..
External/Conceptual Mapping
CONCEPTUAL SCHEMA
CONCEPTUAL LEVEL
Conceptual Internal Mapping
INTERNAL SCHEMA
INTERNAL LEVEL
STORED DATABASE
Elamsri & Navathe, pg 34
Topic 1 : Introduction to Database Technology

26. DBMS Architecture
The Internal Level has an internal schema which describes the physical storage structure of the database.
The Conceptual Level has a conceptual schema which describes the structure of the whole database for a community of users.
The External or View Level includes a number of external schemas or user views. Each external schema describes the part of the database that a particular user group is interested in and hides the rest of the database from that user group.
Topic 1 : Introduction to Database Technology

27. Data Definition Language [ DDL ]
DBMS Languages
Data Definition Language [ DDL ]
This is used to define the conceptual and internal schemas for a database system.
It is not a procedural language, rather a language for describing the types of entities, and the relationships among them in terms of a particular data model.
Data Manipulation Language [ DML ]
This is used to manipulate the database, which typically includes retrieval, insertion, deletion, and modification of the data.
Topic 1 : Introduction to Database Technology

28. DBMS Component Modules (from Elmasri&Navathe pp32)
Topic 1 : Introduction to Database Technology

29. DBMS Utilities Loading Backup File reorganization
To load existing data files into the database
Backup
To create a backup copy of the database, usually by dumping the entire database on tape.
File reorganization
To reorganize a database file in order to improve performance
Topic 1 : Introduction to Database Technology

30. Performance monitoring
DBMS Utilities (ctd.)
Report generation
To generate reports based on the information from the database (including data summaries and computations on data).
Performance monitoring
To provide the DBA with statistical data about the database usage.
Topic 1 : Introduction to Database Technology

31. Classification of DBMS
a) Based on Data Model
Relational [ RDBMS ] Eg. ORACLE, INFORMIX, ACCESS
Network Eg. IDMS (Integrated Database Management systems)
Hierarchical Eg. IMS
Objected Oriented [ OODBMS ] Eg. O2, ObjectStore, Jasmine
b) Based on Number of Users
Single User
Multi User
Topic 1 : Introduction to Database Technology

32. Classification of DBMS
c) Based on ways the database is distributed
Centralized
Distributed
Homogenous
Heterogeneous
Federated
Client/Server
Topic 1 : Introduction to Database Technology

33. Summary - Why Database systems are important
The collection of data is becoming more and more important
The amount of data to be stored is increasing
A good way of managing such data is crucial
Database systems support “ad hoc query” feature which gives answers
to questions on the collection of data
Database systems help to create an environment in which
end-users have better access to better-managed databases
Database systems support an integrated view of the whole
operation of an organisation.
Topic 1 : Introduction to Database Technology

34. DATABASE MODELS Next Lecture ...
Readings : Chpts 5 & 3 Elmasri & Navathe
Topic 1 : Introduction to Database Technology