Advanced Management Information System

Dr. Ebadati

University of Economic Science

پايگاه داده و نحوه طراحي آن

The Traditional Approach Versus

the Database Approach • Traditional approach: separate data files are

created for each application • Results in data redundancy (duplication) • Data redundancy conflicts with data integrity

• Database approach: pool of related data is shared by multiple applications

• Significant advantages over traditional approach

The Traditional Approach Versus the Database Approach (continued)

• The Traditional Approach to Data Management

The Traditional Approach Versus the Database Approach (continued)

• The Database Approach to Data Management

The Traditional Approach Versus the Database Approach (continued)

• Advantages of the Database Approach

The Traditional Approach Versus the Database Approach (continued)

• Advantages of the Database Approach (continued)

The Traditional Approach Versus the Database Approach (continued)

• Disadvantages of the Database Approach

)اطالعاتي(طراحي پايگاه داده اي

. طراحي پايگاه داده اي را مي توان سه مرحله اي در نظر گرفت

.اطالعات شد مدلسازي مفهومي : مرحله اول

پايگاه اطالعاتي است كه مدل مفهومي اطالعات را به توصيف منطقي طراحي منطقي :مرحله دوم

سيستم مديريت (اطالعات به كار فته به وسيله يك سيستم مديريت پايگاه اطالعاتي، تبديل مي كند

) پايگاه اطالعات

پايگاه اطالعاتي است كه توصيف منطقي را به مدل فيزيكي مبدل مي طراحي فيزيك :مرحله سوم

.سازد

پايگاه اطالعاتي موارد مدل منطقي و فيزيكي در حين طراحي زير بايد در نظر گرفته شوند

آتي درآن، تغييراتاطالعاتي با توجه به انعطاف پايگاه

داده ها در پايگاه انسجاماز حفاظتبراي تدابير كنترلي اطالعاتي،

،بهنگام سازي و بازيابي داده هاكارآيي سيستم

ظرفيتهاي ابزارهاي ذخيره سازي كارآيي چگونگي استفاده از .خارجي

طراحي پايگاه اطالعاتي مستلزم شناخت موارد ذيل است

When building a database, consider: • Content: What data should be collected, at what cost? • Access: What data should be provided to which

users, and when? • Logical structure: How should data be arranged to

make sense to a given user? • Physical organization: Where should data be

physically located?

هاي طراحي پايگاه اطالعاتي مروري كلي بر گام

Data Modeling

• Building a database requires two types of design:

• Logical design: Shows an abstract model of how data should be structured and arranged to meet an organization’s information needs

• Physical design: Fine-tunes the logical database design for performance and cost considerations

Data Modeling (continued)

• Data model: a diagram of data entities and

their relationships • Use Case • DFD • Entity-relationship (ER) diagrams: data models that

use basic graphical symbols to show the organization of and relationships between data

هاي طراحي منطقي پايگاه ” ساخته“ اطالعاتي

اطالعات ساختار منطقي و فيزيكيهاي طراحي، ” ساخته“يك پايگاه اطالعاتي را تشريح مي كند ساختار منطقي

:اطالعات از چهار ساخته تشكيل مي شود

عناصر اطالعات

سابقه هاي منطقي

كليدها

روابط

Data Modeling (continued)

• An Entity-Relationship (ER) Diagram for a Customer Order Database

The Relational Database Model

• Relational model: all data elements are placed in two-dimensional tables (relations), which are the logical equivalent of files

• In the relational model: • Each row of a table represents a data entity • Columns of the table represent attributes

• Domain: the allowable values for data attributes

The Relational Database Model

(continued)

عنصر اطالعات

سابقه

سابقه كليد

سابقه كليد

كليد» 1« كليد» 1«

نام مشتري

مشتري

شماره مشتري

مشتري شماره سفارش

شماره مشتري» 1« شماره وضعيت سفارش» 1«

:الف

:ب

:ج

:د

ساخته هاي مدل منطقي اطالعات

رابطه

ها بر قرار مي كند ”سابقه“رابطه، ارتباط ميان •

مياندر مدل مفهومي به رابطه ” موجوديتها“ميان روابط•

.درمدل منطقي تبديل مي شود” ها سابقه“

مشتري شماره مشتري

نام مشتري نشاني پستي خيابان مشتري

محموله نشاني پستي شهر مشتري شماره محموله تاريخ محموله

نام وسيله حمل محموله

سفارش شماره سفارش

شماره وضعيت سفارش» 1« شماره صورتحساب تاريخ صورتحساب

اقالم سفارش شماره سفارش شماره محصول

شماره اقالم سفارش

2 -محصول شماره محصول

متن توصيف محصول

1 -محصول شماره محصول

مبلغ قيمت محصول

كند دريافت مي

ارسال مي شود

در بر دارد

سفارش ها

1 -محصول

2 -محصول

ساختار منطقي اطالعات پايگاه گستر اطالعاتي شركت عدالت

ساختار منطقي اطالعات پايگاه اطالعاتي )ادامه(گستر شركت عدالت

” سفارش“در سابقه ” شماره مشتري“عنصر پيشين در نمودار •

.را معين مي كند” سابقه سفارش“با ” سابقه مشتري“رابطه ميان

نشان دادن رابطه با استفاده از كليد خارجي

مشتري

شماره مشتري

محموله

شماره محموله

تاريخ محموله

شماره مشتري

مشتري

سيستمهاي مديريت پايگاه اطالعاتي

ايجاد پايگاه اطالعاتيرهيافت داده گرا در طراحي سيستم، هدف •

بتوانند آن را مورد استفاده سيستمهاي كاربردي متعدد است كه

.قرار دهند

مدلهاي فيزيكي و منطقي در تركيب با سيستمهاي تنوع احتمالي •

كاربردي متعددي كه احتماالً نياز دسترسي به اطالعات دارند طراحي

.تبديل مي كندمساله بسيار دشواري پايگاه را به

نحوه تعريف نوع داده در پايگاه اطالعات

= ، آغاز= سفارش ، بايت-شماره=نام فيلد

=مشتري ، بايت0=سفارش، سابقه مادر=نام بخش

11=، آغاز 40=مشتري ، بايت-نام=نام فيلد

1=، آغاز 10=مشتري ، بايت-شماره=نام فيلد

=، بايت0=مشتري، سابقه مادر=نام بخش

پايگاه اطالعاتي مشتري، دسترسي=نام شرح پايگاه اطالعاتي

Database Management Systems

(DBMS)

• Interface between • Database and application programs • Database and the user

• Database types • Flat file • Single user • Multiple users

Creating and Modifying the

Database • Data definition language (DDL) • –Collection of instructions/commands that

define and describe data and data relationships in a database

• –Allows database creator to describe the data and the data relationships that are to be contained in the schema and the subschemas

• •Data dictionary: a detailed description of all the data used in the database

Creating and Modifying the

Database (continued) • Using a Data Definition Language to Define a

Schema

Creating and Modifying the

Database (continued) • A Typical Data Dictionary Entry

Storing and Retrieving Data

• When an application requests data from the DBMS, the application follows a logical access path

• When the DBMS goes to a storage device to retrieve the requested data, it follows a path to the physical location (physical access path) where the data is stored

Storing and Retrieving Data

(continued) • Logical and Physical Access Paths

Manipulating Data and

Generating Reports (continued) • Database Output

Popular Database Management

Systems • Popular DBMSs for end users: Microsoft Access

and Corel Paradox • •The complete database management software

market includes databases by IBM, Oracle, and Microsoft

• •Examples of open-source database systems: PostgreSQL and MySQL

• •Many traditional database programs are now available on open-source operating systems

Selecting a Database Management System

• Important characteristics of databases to consider:

• Size of the database • Number of concurrent users • Performance • Ability to be integrated with other systems • Features of the DBMS • Vendor considerations • Cost of the system

Using Databases with Other

Software • Database management systems are often used

with other software packages or the Internet

• A database management system can act as a front-end application or a back-end application

• Front-end application: interacts with users • Back-end application: interacts with applications

g

the Company Database to the Internet

• Corporate databases can be accessed by

customers, suppliers, and employees through: • The Internet • Intranets • Extranets

Distributed & Replicated

Databases • Distributed database

• Data may be spread across several smaller databases connected via telecommunications devices

• Corporations get more flexibility in how databases are organized and used

• Replicated database • Holds a duplicate set of frequently used data

What Is an ERD? • A picture showing the information created, stored,

and used by a business system. • Entities generally represent similar kinds of

information • Lines drawn between entities show relationships

among the data

Using the ERD to Show Business Rules

• Business rules are constraints that are followed when the system is in operation.

• ERD symbols can show when one instance of an entity must exist for an instance of another to exist

• A doctor must exist before appointments for the doctor can be made

Using the ERD to Show Business Rules

• ERD symbols can show when one instance of an entity can be related to only one or many instances of another entity

• One doctor can have many patients; each patient may have only one primary doctor

• ERD symbols show when the existence of an entity instance is optional for a related entity instance

• A patient may or may not have insurance coverage

An ERD Example

ERD Elements

Entity • A person, place, event, or thing about which data is collected • Must be multiple occurrences to be an entity

• Example: If a firm has only one warehouse, the warehouse is not an entity. However, if the firm has several warehouses, the warehouse could be an entity if the firm wants to store data about each warehouse instance.

Entities and Instances

Attributes • Information captured about an entity • Only those used by the organization should be included

in the model • Attribute names are nouns • Sometimes entity name is added at the beginning of the

attribute name for clarity

Identifiers • One or more attributes can serve as the entity identifier,

uniquely identifying each entity instance • Concatenated identifier consists of several attributes • An identifier may be ‘artificial,’ such as creating an ID

number • Identifiers may not be developed until the Design Phase

Choices for Identifiers

Relationships • Associations between entities • The first entity in the relationship is the parent

entity; the second entity in the relationship is the child entity

• Relationships should have active verb names • Relationships go in both directions

Cardinality • Cardinality

• refers to the number of times instances in one entity can be related to instances in another entity

• One instance in an entity refers to one and only one instance in the related entity (1:1)

• One instance in an entity refers to one or more instances in the related entity (1:N)

• One or more instances in an entity refer to one or more instances in the related entity (M:N)

Modality • Modality

• Refers to whether or not an instance of a child entity can exist without a related instance in the parent entity

• Not Null means that an instance in the related entity must exist for an instance in another entity to be valid

• Null means that no instance in the related entity is necessary for an instance in another entity to be valid

M : N Relationships

Data Dictionary Entry for the Patient Entity (Shown Using Erwin)

Un-normalized Entity

Begin with an entity from the logical data model

First Normal Form (1NF)

Look for repeating groups of attributes and remove them into separate entities

Second Normal Form (2NF) If an entity has a concatenated identifier, look for attributes that depend only on part of the identifier. If found, remove to new entity.

Third Normal Form (3NF) Look for attributes that depend only on another non-identifying attribute. If found, remove to new entity. Also remove any calculated attributes.

Summary

• Hierarchy of data: bits, characters, fields, records, files, and databases

• An entity is a generalized class of things (objects) for which data is collected, stored, and maintained

• Attribute: characteristic of an entity • Data model: diagram of entities and relationships

Summary (continued)

• A database management system (DBMS) is a group of programs used as an interface between:

• The database and application programs • The database and the user

• Data dictionary: detailed description of all the data used in the database

References • Charles Parker, Thomas Case. (2000). “Management Information Systems: Action &

Strategy”. (2nd Edition). • Kenneth C. Laudon & Jane P. Laudon (2001). “Management Information Systems:

Managing a Digital Firm”.(7th Edition) • James O’Brien. (1998). “Introduction to Information Systems: A Networked

Enterprise Perspective”. (2nd Edition). • Chris Woodward (2001), CSC Research Services. Creating Information Systems

Harmony (http://www.csc.com/features/2001/21.shtml) • CSC Research Services. “CEOs are from Mars, CIOs are from Pluto”.

(http://www.csc.com/features/2002/22.shtml) • Grover S. Kearns (1997). “Alignment of Information Systems Plans with Business

Plans”. (http://hsb.baylor.edu/ramsower/ais.ac.97/papers/kearns.htm) • Ralph M. Stair & George W. Reynolds (2012). “Fundamentals of Information Systems”. (6th

Edition) • James A. O’Brien, George M. Marakas (2010). “INTRODUCTION TO INFORMATION SYSTEMS”.

(15th Edition) • Ralph Stair, George Reynolds (2006). “Fundamentals of Information Systems”. (3rd /4th Edition). • Stephen Haag, Maeve Cummings (2009). “INFORMATION SYSTEMS ESSENTIALS”. (3rd Edition)

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