Microsoft Word - ch01.doc
16 Pages
English
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Microsoft Word - ch01.doc

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16 Pages
English

Description

  • mémoire - matière potentielle : individuelle
  • revision
Jean Claude TABARY 1993 CHAPITRE 1: L'EVOLUTION DES CONCEPTIONS EPISTEMOLOGIQUES Le sens commun estime raisonnable d'attribuer la plupart de nos sensations à des causes qui agissent de l'extérieur sur nos corps. Il ne croit pas que la chambre où nous sommes assis cesse d'exister dès que nous fermons les yeux ou allons nous coucher. Il ne croit pas que notre femme ou nos enfants sont de purs produits de notre imagination. En cela, nous pouvons être d'accord avec le sens commun; mais où il a tort, c'est lorsqu'il suppose que les objets ressemblent intrinsèquement aux perceptions qu'ils causent.
  • réalisme de natures
  • évolution socioculturelle du groupe
  • sens de la mécanique quantique
  • réalismes
  • réalisme
  • réalité
  • réalités
  • analyses
  • analyse
  • connaissances
  • connaissance
  • structure
  • structures
  • environnements
  • environnement
  • référence
  • références

Subjects

Informations

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Reads 17
Language English
Document size 4 MB

Exrait

Database Systems
Dr . Hamid R. Nemati
4
4
4
4
4
4
l
l
l
l
these entities are related.
It provides a description of the way in which
contains data.
It specifies the entities about which the database
Databasesneeded information. and
File SystemsIt is used by the decision maker to recall the Databases
Intro to
A conceptual data model.
Database
database models
Understand three different types of
Understand basic database concepts
systems
Understand characteristics of database
Understand advantages of using a database
Understand characteristics of a file system
Databasesdatabases and
File Systems
DatabasesUnderstand the basics of data and
Intro to
Objectives
Bryan School of Business and Economics
Operations Management
Department of Information Systems and
ISM 318:
Databases
and
File Systems
Databases
Intro toField
l
u Raw, unsummarized , and unanalyzed facts
l
u Data processed into a meaningful form
u One person's information can be another's data
l
u Knowing what information is required
u Knowing what the information means
Hierarchy of Data
“Raw” facts that have little meaning unless they have been
organized in some logical manner. The smallest piece of data
such as the letter A, the number 5, or some symbol such as;
sales value, and so on.
Rudd’s name, address, phone number, date of birth, credit limit,
A collection of related records. For example, a file might contain
Gigantic University.
Hierarchy of Data
Database
Project database
Database File Database File Database File
Personal File Department File
Record 1 Record 2 Record 3
Field 1 Field 2
Payroll File
Databases
and
File Systems
Databases
Intro to
contain the records for the students currently enrolled at
data about ROBCOR Company’s vendors; or, a file might
File
unpaid balance, and so on.
record for a customer named J. D. Rudd might consist of J. D.
person, place, or thing. For example, the fields that comprise a
A logically connected set of one or more fields that describes a Record
numbers, a birth date, a customer name, a year-to-date (YTD)
has a specific meaning. A field might define a telephone
A character or group of characters (alphabetic or numeric) that
Databases> * +. A single character requires one byte of computer storage.
and
‘ ? File Systems
Databasesthat can be “recognized” by the computer is a single character,
Intro to
Data
Knowledge
DatabasesInformation
and
File Systems
Databases
Intro to
Data
Data, information, and knowledgel
u Is used when working with a SINGLE database file
l
u A collection of interrelated data and a collection of
programs that provide access to the data.
u The primary goal of a DBMS is to provide an
environment which is both convenient and efficient
to use in retrieving information from and storing
information into the database.
Functions of DBMS
l
l
l
l
u Data Redundancy
u Data Inconsistency
u Data Dependency
u Data Integrity
u Data Security
Issues to consider when dealing with DBMS
DatabasesGeneration of reports and forms
and
File SystemsProcessing data Databases
Intro to
Storage and Retrieval of data
Databases
and
File Systems
Databases
Intro to
File System Designs
Contrasting Database and
DatabasesDatabase Management Systems (DBMS)
and
File Systems
Databases
Intro to
File Processing Systems (FPS)
Database Managersl
u It helps make data management more efficient and
effective.
u Its query language allows quick answers to ad hoc
queries.
u It provides end users better access to more and
better-managed data.
u It promotes an integrated view of organization’s
operations -- “big picture”.
u It reduces the probability of inconsistent data.
The DBMS Manages the Interaction
between the End User and the Database
File System Critique
l
u File systems require extensive programming in 3GL.
u As file systems become more complex, managing
files gets more difficult.
u Making changes in existing file structures is
important and difficult.
u Data access programs are subject to change with file
structure changes (structural dependence).
u Security features are difficult to implement and are
lacking.
Databases
and
File Systems
Databases
Intro to
File System Data Management
Databases
and
File Systems
Databases
Intro to
Databases
and
File Systems
Databases
Intro to
Importance of DBMS
Introducing the Databaseî
î
File System Critique
l
u Structural Dependence
A change in any file’s structure requires the modification
of all programs using that file.
u Data Dependence
A change in any file’s data characteristics requires
changes of all data access programs.
u Data dependence makes file systems extremely
cumbersome from a programming and data
management point of view.
File System Critique
l
u A good (flexible) record definition anticipates
reporting requirements by breaking up fields into
their components.
l Example:
v Last Name, First Name, Initial
v Customer Address
u Selecting proper field names is very important.
l Descriptive
l Self-documenting
File System Critique
l
u Data Inconsistency (lack of data integrity)
u Data anomalies
l Modification anomalies
l Insertion anomalies
l Deletion anomalies
Databases
and
File Systems
DatabasesUncontrolled data redundancy sets the stage for
Intro to
Data Redundancy:
Street Address, City, State
Customer Name
Databases
and
File Systems
Databases
Intro to
Field Definitions and Naming Conventions
Databases
and
File Systems
Databases
Intro to
Structural and Data DependenceDatabase Systems
l
l
l
l
l
Database Systems Environment
Database Systems
l
u Hardware
l Computer
l Peripherals
u Software
l Operating systems software
l DBMS software
l Applications programs and utilities software
Databases
and
File Systems
Databases
Intro to
The Database System Components
Databases
and
File Systems
Databases
Intro to
access paths.
DBMS takes care of defining all the required
but also the relationships.
Current DBMS stores not only the data structure,
data structural dependency problems.
system’s data inconsistency, data anomalies, and
DBMS makes it easier to eliminate most of the file
user data are stored, accessed, and managed.
Databases
The database represents a change in the way end and
File Systems
Databasesstored in a single data repository.
Intro to
In a database system, logically related data areDatabase Systems
l
u People
l Systems administrators
l Database administrators
l Database designers
l Systems analysts and programmers
l End users
u Procedures
l Instructions and rules that govern the design and use of the
database system
u Data
l Collection of facts stored in the database
Database Systems
l
u The complexity of database systems depends on
various organizational factors:
l Organization’s size
l Organization’s function
l Organization’s corporate culture
l Organizational activities and environment
u Database solutions must be cost effective and
strategically effective.
Database Systems
l
u Number of Users
l Single-user
l Multi-user
u Scope
l Desktop
l Workgroup
l Enterprise
Databases
and
File Systems
Databases
Intro to
Types of Database Systems
Databases
and
File Systems
Databases
Intro to
Database Systems and Organizational Factors
Databases
and
File Systems
Databases
Intro to
The Database System ComponentsDatabase Systems
l
u Location
l Centralized
l Distributed
u Use
l Transactional (Production)
l Decision support
l Data warehouse
Database Systems
l
u Data Dictionary Management
l Data dictionary stores definitions of the data elements and
their relationships ( metadata ).
l It provides data abstraction and removes structural and data
dependency from the system.
u Data Storage Management
l DBMS creates data storage structure and relieves us from
the task of defining and programming physical data
characteristics.
Database Systems
l
u Data Transformation and Management
l DBMS relieves us from the chore of making distinction
between logical format and physical format of data.
u Security Management
l DBMS provides user security and data privacy within the
database.
l Data security is especially important in multi-user database.
Databases
and
File Systems
Databases
Intro to
DBMS Functions
Databases
and
File Systems
Databases
Intro to
DBMS Functions
Databases
and
File Systems
Databases
Intro to
Types of Database Systems.
A
.
Database Systems
l
u Multi-User Access Control
l DBMS ensures that multiple users can access the database
concurrently and still guarantees the integrity of the
database.
u Backup and Recovery Management
l DBMS provides backup and recovery procedures to ensure
data safety and integrity.
u Data Integrity Management
l DBMS promotes and enforces integrity rules to eliminate
data integrity problems.
l Ensuring data integrity is especially important in
transaction-oriented database systems.
l
u A poorly designed database is a breeding ground for
uncontrolled data redundancies
u A poorly designed database generates errors that
lead to bad decisions
l
u Focus on principles and concepts of practical
database design
u Use of two complete applications through the logical
design stage
Database Models
l logical
l
u Conceptual models focus on the logical nature of
the data representation. They are concerned with
what is represented rather than how it is represented.
u Implementation models place the emphasis on how
the data are represented in the database or on how
the data structures are implemented.
Two Categories of Database Models
Databases
andthe data relationships found within the database.
File Systems
Databases the data structure and represent constructs used to
Intro to
is a collection of database model
A Practical Approach to Database Design
Databases
and
File Systems
Databases
Intro to
Why Database Design Is Important?
Introducing the Database
Databases
and
File Systems
Databases
Intro to
DBMS Functions Database Models
l
u One-to-many relationships
Database Models
l
u Many-to-many relationships
Database Models
l
u One-to-one relationships
Databases
and
File Systems
DatabasesDatabase Models
Intro to
Three Types of Relationships in Conceptual
Databases
and
File Systems
DatabasesDatabase Models
Intro to
Three Types of Relationships in Conceptual
Databases
and
File Systems
DatabasesDatabase Models
Intro to
Three Types of Relationships in Conceptual