Database management systems (initiation)

1. 

Introduction
Med.elhedhli@mailpost.tn
Mohamed HEDHLY

2.  Presentation
 Examples
 Characteristics
 Data independence
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•

Data models
•
•
•
•

Physical independence
Logical independence
Hierarchical model
Network model
Relational model
Object-oriented model
Data architecture
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•
•
External level
Logical level
Internal level

3.  Database
management systems is a
software package that allows users to
create, edit, query, update and administrate
Database
 it also defines rules to validate and
manipulate this data.
 Using DBMS final users can simply store
modify extract information from database.

5. 

Characteristics

7.  Data
independence is a form of database
management that keeps data separated
from all programs that make use of it.
 Data cannot be redefined or reorganized by
any of the programs that make use of it. In
this manner, the data remains accessible,
but it is also stable and cannot be corrupted
by the applications

8. It is the ability to change the internal
schema(Using new storage media, Using
different data structures, switching from one
access method to another, using different file
organizations or storage structures, modifying
indexes, ...) for reasons of optimization or
reorganization
without
affecting
the
application programs.

9. Logical data independence makes it
possible to change the structure of the
data(addition or deletion of fresh entities,
attributes
or
relationships...
)
independently
of
modifying
the
applications or programs that make use
of the data.

11. It’s a collection of concepts, rules and
tools for the description of the structure
of the database.
Structure of the database means the
data types, the data semantics, the
constraints and the relationships for the
description
or
storage
of
data
respectively.

12. The hierarchical data
model organizes data in
a tree structure
 each entity has only one
parent but can have
several children . At the
top of hierarchy there is
only one entity which is
called Root.


13. In the network model,
entities are organized in
a graph, in which some
entities can be accessed
through several path
 The
network
model
organizes data in a tree
structure but allows each
record to have multiple
parent and child records


14. 

A
relational
database
allows the definition of
data structures, storage
and retrieval operations
and integrity constraints.
the data and relations
between
them
are
organized in tables.
A table is a collection of
records and each record in
a table contains the same
fields.

15.  Object-oriented
models
define a database as a
collection of objects
with
features
and
methods.
 information
is
represented in the
form of objects as used
in
object-oriented
programming

17. Models, policies, rules or standards that
govern which data is collected, and how it is
stored, arranged, integrated, and put to use in
data systems and in organizations
The architecture of a database system
determines its capability, reliability,
effectiveness and efficiency in meeting user
requirements.
A database management system provides
three views of the database data:

18. 

The highest level of
abstraction it define and
specify user views : views
that enable different data
users to see it in different
ways
It also contains the method
of deriving the objects in
the external view from the
objects in the conceptual
view.

19. 


The next-higher level of
abstraction describes what
data are stored in the
database,
and
what
relationships exist among
those data.
It defines how information
is arranged within the
database.
the conceptual schema
describes all relations that
are stored in the database

20. 



The
lowest
level
of
abstraction
It describes how the data will
be physically stored and
accessed, using a DBMS.
So it describes details of how
data is stored: files, indices,
etc. on the random access
disk system.
It also typically describes the
record layout of files and type
of files