Database Concepts.ppt

Introduction to DB
Introduction and
Conceptual Modeling

Objectives
Some common uses of database systems.
File-based systems.
Typical functions of a DBMS.
Major components of the DBMS
environment.
History of the development of DBMSs.
Advantages and disadvantages of
DBMSs
Three-level architecture

Examples of Database
Applications
Purchases from the supermarket
Purchases using your credit card
Booking a holiday at the travel agents
Using the local library
Taking out insurance
Using the Internet
Studying at university
Many more …….

Types of Databases and
Database Applications
Numeric and Textual Databases
Multimedia Databases
Geographic Information Systems (GIS)
Data Warehouses
Real-time and Active Databases
A number of these databases and applications are
described later in the book (see Chapters 24,28,29)

File-Based Systems
Collection of application programs that
perform services for the end users (e.g.
reports).
Each program defines and manages its
own data.

Limitations of File-Based
Approach
Separation and isolation of data
– Each program maintains its own set of data.
– Users of one program may be unaware of
potentially useful data held by other programs.
Duplication of data
– Same data is held by different programs.
– Wasted space and potentially different values
and/or different formats for the same item.

Basic Definitions
Database: A collection of related data.
Database Management System
(DBMS): A software package/ system to
facilitate the creation and maintenance of
a computerized database.
Database System: The DBMS software
together with the data itself. Sometimes,
the applications are also included.

Database Management System
(DBMS)

Typical DBMS Functionality
 Define a database : in terms of data types,
structures and constraints
 Construct or Load the Database on a
secondary storage medium
 Manipulating the database : querying,
generating reports, insertions, deletions and
modifications to its content
 Concurrent Processing and Sharing by a set
of users and programs – yet, keeping all data
valid and consistent

Typical DBMS Functionality
Other features:
– Protection or Security measures to
prevent unauthorized access
– “Active” processing to take internal
actions on data
– Presentation and Visualization of data

Components of DBMS
Environment
 Hardware
– PC, workstation, mainframe, a network of
computers.
 Software
– DBMS, operating system, network software (if
necessary) and also the application programs.
 Data
– Used by the organization and a description of this
data called the schema.
 Procedures
– Instructions and rules that should be applied to the
design and use of the database and DBMS.
 People

Roles in the Database
Environment
Data Administrator (DA)
Database Administrator (DBA)
Database Designers (Logical and
Physical)
Application Programmers
End Users (naive and sophisticated)

Example of a Database
(with a Conceptual Data Model)
 Mini-world for the example: Part of a
UNIVERSITY environment.
 Some mini-world entities:
– STUDENTs
– COURSEs
– SECTIONs (of COURSEs)
– (academic) DEPARTMENTs
– INSTRUCTORs
Note: The above could be expressed in the ENTITY-
RELATIONSHIP data model.

Example of a Database
(with a Conceptual Data Model)
 Some mini-world relationships:
– SECTIONs are of specific COURSEs
– STUDENTs take SECTIONs
– COURSEs have prerequisite COURSEs
– INSTRUCTORs teach SECTIONs
– COURSEs are offered by DEPARTMENTs
– STUDENTs major in DEPARTMENTs
Note: The above could be expressed in the ENTITY-
RELATIONSHIP data model.

Main Characteristics of the
Database Approach
 Self-describing nature of a database system: 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.
 Insulation between programs and data: Called
program-data independence. Allows
changing data storage structures and operations
without having to change the DBMS access
programs.

Database Approach
 Data Abstraction: A data model is used to
hide storage details and present the users with
a conceptual view of the database.
 Support of multiple views of the data: Each
user may see a different view of the
database, which describes only the data of
interest to that user.

Database Approach
 Sharing of data and multiuser transaction
processing : allowing a set of concurrent users to
retrieve and to update the database. Concurrency
control within the DBMS guarantees that each
transaction is correctly executed or completely
aborted. OLTP (Online Transaction Processing) is
a major part of database applications.

Advantages of Using the
Database Approach
Controlling redundancy in data storage and
in development and maintenence efforts.
Sharing of data among multiple users.
Restricting unauthorized access to data.
Providing persistent storage for program
Objects (in Object-oriented DBMS’s – see
Chs. 20-22)
Providing Storage Structures for efficient
Query Processing

Advantages of Using the
Database Approach
 Providing backup and recovery services.
 Providing multiple interfaces to different
classes of users.
 Enforcing integrity constraints on the
database.
 Drawing Inferences and Actions using rules

Disadvantages of DBMSs
Complexity
Size
Cost of DBMS
Additional hardware costs
Cost of conversion
Performance
Higher impact of a failure

Historical Development of
Database Technology
 Early Database Applications: The
Hierarchical and Network Models were
introduced in mid 1960’s and dominated
during the seventies. A bulk of the worldwide
database processing still occurs using these
models.
 Relational Model based Systems: The
model that was originally introduced in 1970
was heavily researched and experimented
with in IBM and the universities. Relational
DBMS Products emerged in the 1980’s.

Historical Development of
Database Technology
 Object-oriented applications: OODBMSs were
introduced in late 1980’s and early 1990’s to cater to
the need of complex data processing in CAD and
other applications. Their use has not taken off much.
 Data on the Web and E-commerce Applications:
Web contains data in HTML (Hypertext markup
language) with links among pages. This has given
rise to a new set of applications and E-commerce is
using new standards like XML (eXtended Markup
Language).

Extending Database
Capabilities
 New functionality is being added to
DBMSs in the following areas:
– Scientific Applications
– Image Storage and Management
– Audio and Video data management
– Data Mining
– Spatial data management
– Time Series and Historical Data Management
The above gives rise to new research and development in
incorporating new data types, complex data structures, new
operations and storage and indexing schemes in database
systems.

When not to use a DBMS
 Main inhibitors (costs) of using a DBMS:
– High initial investment and possible need for
additional hardware.
– Overhead for providing generality, security,
concurrency control, recovery, and integrity
functions.
 When a DBMS may be unnecessary:
– If the database and applications are simple, well
defined, and not expected to change.
– If there are stringent real-time requirements that
may not be met because of DBMS overhead.
– If access to data by multiple users is not required.

When not to use a DBMS
When no DBMS may suffice:
– If the database system is not able to handle the
complexity of data because of modeling
limitations
– If the database users need special operations not
supported by the DBMS.

Database Concepts.ppt

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