第六章 数据设计

1、School of Information TechnologyJiangxi University of Finance & Economics2008Chapter 6 Data Design Information Systems Analysis and Design 2System PlanningSystem AnalysisSystem DesignSystem ImplementationSystem Operation & SupportPhase DescriptionData DesignUser Interface, Input, and output designSy

2、stem ArchitectureInformation Systems Analysis and Design 3Phase DescriptionlSystems Design is the third of five phases in the systems development life cycle (SDLC)lNow you are ready to begin the physical design of the system that will meet the specifications described in the system requirements docu

3、mentlSystems design tasks include data design, user interface design, and system architectureInformation Systems Analysis and Design 4Chapter ContentsWeb-Based Database DesignData Design TerminologySteps in Database DesignNormalizationData StorageData Design ConceptsInformation Systems Analysis and

4、Design 5Chapter Objectives lExplain data design concepts and data structureslDescribe file processing systems and various types of fileslUnderstand database systems and define the components of a database management system (DBMS)lDescribe Web-based data design and characteristics Information Systems

5、 Analysis and Design 6Chapter ObjectiveslExplain data design terminology, including entities, fields, common fields, records, files, tables, and key fieldslDescribe data relationships, draw an entity-relationship diagram, define cardinality and use cardinality notationlExplain the concept of normali

6、zationlUnderstand the steps in database designInformation Systems Analysis and Design 7Chapter ObjectiveslDescribe hierarchical, network, relational, and object-oriented database modelslExplain data warehousing/data mininglDifferentiate between logical and physical storage and recordslExplain data c

7、ontrol measuresInformation Systems Analysis and Design 8IntroductionlYou will develop a physical plan for data organization, storage, and retrievallBegins with a review of data design concepts and terminology, then discusses file-based systems and database systems, including Web-based databaseslConc

8、ludes with a discussion of data mining, data warehousing, physical design issues, logical and physical records, data storage formats, and data controlsInformation Systems Analysis and Design 9Data Design ConceptslBefore constructing an information system, a systems analyst must understand basic desi

9、gn concepts, including data structures and the characteristics of file-oriented and database systems, including Web-based database designInformation Systems Analysis and Design 10Data Design ConceptslData StructuresA file or table contains data about people, places or events that interact with the s

10、ystemFile-oriented systemFile processingDatabase systemInformation Systems Analysis and Design 11Data Design ConceptslOverview of File ProcessingSome companies use file processing to handle large volumes of structured dataAlthough less common today, file processing can be more efficient and cost les

11、s than a DBMS in certain situationsInformation Systems Analysis and Design 12Data Design ConceptslOverview of File ProcessingPotential problems lData redundancylData integritylRigid data structureInformation Systems Analysis and Design 13Data Design ConceptslOverview of File ProcessingUses various t

12、ypes of fileslMaster filelTable filelTransaction filelWork file scratch filelSecurity filelHistory fileInformation Systems Analysis and Design 14Data Design ConceptslOverview of Database SystemsA properly design database system offers a solution to the problems of file processingProvides an overall

13、framework that avoids data redundancy and supports a real-time, dynamic environmentInformation Systems Analysis and Design 15Data Design ConceptslOverview of Database SystemsA database management system (DBMS) is a collection of tools, features, and interfaces that enables users to add, update, mana

14、ge, access, and analyze the contents of a databaseThe main advantage of a DBMS is that it offers timely, interactive, and flexible data accessInformation Systems Analysis and Design 16Data Design ConceptslOverview of Database SystemsAdvantageslScalabilitylBetter support for client/server systemslEco

15、nomy of scalelFlexible data sharinglEnterprise-wide application database administrator (DBA)lStronger standardsInformation Systems Analysis and Design 17Data Design ConceptslOverview of Database SystemsAdvantageslControlled redundancylBetter securitylIncreased programmer productivitylData independen

16、ceInformation Systems Analysis and Design 18Data Design ConceptslDatabase TradeoffsBecause DBMSs are powerful, they require more expensive hardware, software, and data networks capable of supporting a multiuser environmentMore complex than a file processing systemProcedures for security, backup, and

17、 recovery are more complicated and criticalInformation Systems Analysis and Design 19Web-Based Database DesignlThe following sections discuss the characteristics of Web-based design, Internet terminology, connecting a database to the Web, and data security on the WebInformation Systems Analysis and

18、Design 20Web-Based Database DesignlCharacteristics of Web-Based DesignIn a Web-based design, the Internet serves as the front end, or interface for the database management system. Internet technology provides enormous power and flexibilityWeb-based systems are popular because they offer ease of acce

19、ss, cost-effectiveness, and worldwide connectivityInformation Systems Analysis and Design 21Web-Based Database DesignlInternet TerminologyWeb browserWeb pageHTML Hypertext Markup LanguageWeb serverWeb siteIntranetInformation Systems Analysis and Design 22Web-Based Database DesignlInternet Terminolog

20、yExtranetProtocolsWeb-centricClientsServersInformation Systems Analysis and Design 23Web-Based Database DesignlConnecting a Database to the WebDatabase must be connected to the Internet or intranetlMiddlewarelMacromedias ColdFusionInformation Systems Analysis and Design 24Web-Based Database DesignlD

21、ata SecurityWeb-based data must be totally secure, yet easily accessible to authorized usersTo achieve this goal, well-designed systems provide security at three levels: the database itself, the Web server, and the telecommunication links that connect the components of the systemInformation Systems

22、Analysis and Design 25Data Design TerminologylDefinitionsEntityTable or fileFieldlAttributelCommon fieldRecordlTupleInformation Systems Analysis and Design 26Data Design TerminologylKey FieldsPrimary keylCombination keylComposite keylConcatenated keylMulti-valued keyInformation Systems Analysis and

23、Design 27Data Design TerminologylKey FieldsCandidate keylNonkey fieldForeign keySecondary keyInformation Systems Analysis and Design 28Data Design TerminologylReferential IntegrityValidity checks can help avoid data input errorsIn a relational database, referential integrity means that a foreign key

24、 value cannot be entered in one table unless it matches an existing primary key in another tableInformation Systems Analysis and Design 29NormalizationlNormalizationlTable designlInvolves four stages: unnormalized design, first normal form, second normal form, and third normal formlMost business-rel

25、ated databases must be designed in third normal formInformation Systems Analysis and Design 30Steps in Database DesignvCreate the initial ERDvAssign all data elements to entitiesvCreate 3NF designs for all tables, taking care to identify all primary, secondary, and foreign keysvVerify all data dicti

26、onary entrieslAfter creating your final ERD and normalized table designs, you can transform them into a databaseInformation Systems Analysis and Design 31Database ModelslHierarchical and Network DatabasesIn a hierarchical database, data is organized like a family tree or organization chart, with bra

27、nches representing parent records and child recordsA network database resembles a hierarchical design, but provides somewhat more flexibilityInformation Systems Analysis and Design 32Database ModelslRelational DatabasesThe relational model was introduced during the 1970s and became popular because i

28、t was flexible and powerfulBecause all the tables are linked, a user can request data that meets specific conditionsNew entities and attributes can be added at any time without restructuring the entire databaseInformation Systems Analysis and Design 33Database ModelslRelational DatabasesInformation

29、Systems Analysis and Design 34Database ModelslRelational DatabasesInformation Systems Analysis and Design 35Database ModelslObject-Oriented DatabasesMany systems developers are using object-oriented database (OODB) design as a natural extension of the object-oriented analysis processlObject data sta

30、ndardlObject Database Management Group (ODMG)lEach object has a unique object identifierInformation Systems Analysis and Design 36Data StoragelData WarehousingData warehouse - dimensionsWithout a data warehouse it would be difficult for a user to extract data that spans several information systems a

31、nd time framesAllows users to retrieve and analyze the data easilyInformation Systems Analysis and Design 37Data StoragelData MiningWorks best when you have clear, measurable goalslIncrease average pages viewed per session.lIncrease number of referred customerslReduce clicks to closelIncrease checko

32、uts per visitlIncrease average profit per checkoutInformation Systems Analysis and Design 38Data StoragelLogical and Physical StorageLogical storagelAs seen through a users eyeslCharacters lDate element or data itemlLogical recordPhysical storagelHardware-relatedlPhysical record or blocklBlocking fa

33、ctorInformation Systems Analysis and Design 39Data StoragelData Storage FormatsBinary digitsBitByteEBCDIC and ASCIIUnicodeInformation Systems Analysis and Design 40Data StoragelData Storage FormatsBinarylBinary storage formatlInteger formatlLong integer formatlOther binary formats exist for efficien

34、t storage of exceedingly long numbersInformation Systems Analysis and Design 41Data StoragelSelecting a Data Storage FormatIn many cases, a user can select a specific data storage formatFor example, when using Microsoft Office, you can store documents, spreadsheets, and databases in Unicode-compatib

35、le form by using the font called Arial Unicode MSBest answer is it depends on the situationInformation Systems Analysis and Design 42Data StoragelDate FieldsMost date formats now are based on the model established by the International Organization for Standardization (ISO)Can be sorted easily and us

36、ed in comparisonsAbsolute dateBest method depends on how the specific date will be printed, displayed or used in a calculationInformation Systems Analysis and Design 43Data ControllFile and database control must include all measures necessary to ensure that data storage is correct, complete, and securelA well-designed DBMS must provide built-in control and security features, including subschemas, passwords, encryption, audit trail files, and backup and recovery procedures to maintain dataInformation Systems Analysis and Design 44Data C