Dr. Ebadati University of Economic Science

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1 Advanced Management Information System Dr. Ebadati University of Economic Science

2 پايگاه داده و نحوه طراحي ا ن

3 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

4 The Traditional Approach Versus the Database Approach (continued) The Traditional Approach to Data Management

5 The Traditional Approach Versus the Database Approach (continued) The Database Approach to Data Management

6 The Traditional Approach Versus the Database Approach (continued) Advantages of the Database Approach

7 The Traditional Approach Versus the Database Approach (continued) Advantages of the Database Approach (continued)

8 The Traditional Approach Versus the Database Approach (continued) Disadvantages of the Database Approach

9 طراحي پايگاه داده اي (اطلاعاتي ( طراحي پايگاه داده اي را مي توان سه مرحله اي در نظر گرفت. مرحله اول: مدلسازي مفهومي اطلاعات شد. مرحله دوم: طراحي منطقي پايگاه اطلاعاتي است كه مدل مفهومي اطلاعات را به توصيف منطقي اطلاعات به كار فته به وسيله يك سيستم مديريت پايگاه اطلاعاتي تبديل مي كند (سيستم مديريت پايگاه اطلاعات ( مرحله سوم: طراحي فيزيك پايگاه اطلاعاتي است كه توصيف منطقي را به مدل فيزيكي مبدل مي سازد.

10 در حين طراحي مدل منطقي و فيزيكي پايگاه اطلاعاتي موارد زير بايد در نظر گرفته شوند انعطاف پايگاه اطلاعاتي با توجه به تغييرات ا تي درا ن تدابير كنترلي اطلاعاتي براي حفاظت انسجام از داده ها در پايگاه كارا يي سيستم بهنگام سازي و بازيابي داده ها كارا يي چگونگي استفاده از ظرفيتهاي ابزارهاي ذخيره سازي خارجي.

11 طراحي پايگاه اطلاعاتي 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?

12 مروري كلي بر گامهاي طراحي پايگاه اطلاعاتي

13 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

14 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

15 ساخته هاي طراحي منطقي پايگاه اطلاعاتي ساخته هاي طراحي ساختار منطقي و فيزيكي اطلاعات يك پايگاه اطلاعاتي را تشريح مي كند ساختار منطقي اطلاعات از چهار ساخته تشكيل مي شود: عناصر اطلاعات سابقه هاي منطقي كليدها روابط

16 Data Modeling (continued) An Entity-Relationship (ER) Diagram for a Customer Order Database

17 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

18 The Relational Database Model (continued)

19 ساخته هاي مدل منطقي اطلاعات الف : عنصر اطلاعات نام مشتري سابقه مشتري ب : ج : سابقه كليد شماره مشتري سابقه مشتري د : كليد شماره سفارش «1» شماره مشتري «1» كليد «1» شماره وضعيت سفارش «1» كليد

20 رابطه رابطه ارتباط ميان سابقه ها بر قرار مي كند ميان روابط موجوديتها در مدل مفهومي به رابطه ميان ها سابقه درمدل منطقي تبديل مي شود.

21 ساختار منطقي اطلاعات پايگاه اطلاعاتي شركت عدالتگستر مشتري سفارش شماره سفارش «1» شماره وضعيت سفارش شماره صورتحساب تاريخ صورتحساب در بر دارد دريافت ميكند محموله شماره محموله تاريخ محموله نام وسيله حمل محموله شماره مشتري نام مشتري نشاني پستي خيابان مشتري نشاني پستي شهر مشتري اقلام سفارش ارسال مي شود شماره سفارش شماره محصول شماره اقلام سفارش محصول - 2 شماره محصول متن توصيف محصول محصول - 1 سفارش ها محصول - 1 شماره محصول مبلغ قيمت محصول محصول - 2

22 ساختار منطقي اطلاعات پايگاه اطلاعاتي شركت عدالتگستر (ادامه) سفارش در نمودار عنصر پيشين شماره مشتري در سابقه رابطه ميان سابقه مشتري با سابقه سفارش را معين مي كند.

23 نشان دادن رابطه با استفاده از كليد خارجي مشتري شماره مشتري محموله شماره محموله تاريخ محموله شماره مشتري مشتري

24 سيستمهاي مديريت پايگاه اطلاعاتي هدف رهيافت داده گرا در طراحي سيستم ايجاد پايگاه اطلاعاتي است كه سيستمهاي كاربردي متعدد بتوانند ا ن را مورد استفاده قرار دهند. تنوع احتمالي مدلهاي فيزيكي و منطقي در تركيب با سيستمهاي كاربردي متعددي كه احتمالا نياز دسترسي به اطلاعات دارند طراحي پايگاه را به مساله بسيار دشواري تبديل مي كند.

25 نحوه تعريف نوع داده در پايگاه اطلاعات شرح پايگاه اطلاعاتي بخش نام=پايگاه اطلاعاتي مشتري دسترسي نام=مشتري سابقه مادر= 0 بايت= ا غاز= 1 فيلد نام=شماره-مشتري بايت= 10 ا غاز= 11 فيلد نام=نام-مشتري بايت= 40 بخش نام=سفارش سابقه مادر= 0 مشتري بايت= ا غاز= فيلد نام=شماره-سفارش بايت=

26 Database Management Systems (DBMS) Interface between Database and application programs Database and the user Database types Flat file Single user Multiple users

27 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

28 Creating and Modifying the Database (continued) Using a Data Definition Language to Define a Schema

29 Creating and Modifying the Database (continued) A Typical Data Dictionary Entry

30 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

31 Storing and Retrieving Data (continued) Logical and Physical Access Paths

32 Manipulating Data and Generating Reports (continued) Database Output

33 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

34 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

35 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

36 the Company Database to the Internet Corporate databases can be accessed by customers, suppliers, and employees through: The Internet Intranets Extranets

37 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

38 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

39 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

40 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

41 An ERD Example

42 ERD Elements

43 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.

44 Entities and Instances

45 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

46 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

47 Choices for Identifiers

48 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

49 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)

50 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

51 M : N Relationships

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

53 Un-normalized Entity Begin with an entity from the logical data model

54 First Normal Form (1NF) Look for repeating groups of attributes and remove them into separate entities

55 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.

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

57 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

58 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

59 References Charles Parker, Thomas Case. (2000). Management Information Systems: Action & Strategy. (2 nd Edition). Kenneth C. Laudon & Jane P. Laudon (2001). Management Information Systems: Managing a Digital Firm.(7 th Edition) James O Brien. (1998). Introduction to Information Systems: A Networked Enterprise Perspective. (2 nd Edition). Chris Woodward (2001), CSC Research Services. Creating Information Systems Harmony ( CSC Research Services. CEOs are from Mars, CIOs are from Pluto. ( Grover S. Kearns (1997). Alignment of Information Systems Plans with Business Plans. ( Ralph M. Stair & George W. Reynolds (2012). Fundamentals of Information Systems. (6 th Edition) James A. O Brien, George M. Marakas (2010). INTRODUCTION TO INFORMATION SYSTEMS. (15 th Edition) Ralph Stair, George Reynolds (2006). Fundamentals of Information Systems. (3 rd /4 th Edition). Stephen Haag, Maeve Cummings (2009). INFORMATION SYSTEMS ESSENTIALS. (3 rd Edition)

60 موفق باشيد

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3--03 جلسه ي بيست و سوم دانشگاه شهيد بهشتي دانشكدهي مهندسي برق و كامپيوتر بهار 392 احمد محمودي ازناوه http://faculties.sbu.ac.ir/~a_mahmoudi/ فهرست مطالب مروري بر جلسهي پيش مثال حافظهي نهان چند سطحي حافظهي