高等教育出版社影印版计算机专业英语习题ch_13_im

1、Ch 13 Systems Analysis and DesignLecture OutlineCompetencies pg 356Describe the six phases of the systems life cycleIdentify information needs and formulate possible outcomesAnalyze existing information systems and evaluate the feasibility of alternative systemsIdentify, acquire, and test new system

2、 software and hardwareSwitch from an existing information system to a new one with minimal riskPerform system audits and periodic evaluationsIntroduction pg 357It takes considerable time and effort to create a system that is truly useful.History has many examples of where systems were not implemente

3、d properly, such as a General Motors $40 billion attempt to automate assembly lines, and an Internal Revenue Services attempt to automate tax returnsCompetent end users need to understand the importance of systems analysis and designThey need to know the six phases of the system life cycle:Prelimina

4、ry investigationSystems analysisSystems designSystems developmentSystems implementation, andSystems maintenance Systems Analysis and Design pg 358A system is a collection of activities and elements organized to accomplish a goalAn Information system is a collection of hardware, software, people, pro

5、cedures, and dataOrganizations need to change their information systems when they go through changes such as:organizational growth, mergers and acquisitions, new marketing opportunities, revisions in governmental regulations, and the availability of new technologySystems analysis and design is a six

6、 phase problem-solving procedure for examining and improving an information system. Steps include:Preliminary investigation: problems & needs are identifiedSystems analysis: present system studied, new requirements specifiedSystems design: new or alternative system is plannedSystems development: new

7、 hardware & software are acquired, developed, and testedSystems implementation: new system installed and people trained to use itSystems maintenance: ongoing improvements and updatesSystems analysts are the key people that utilize these phases to develop systemsMany times end users develop there own

8、 systems since there is a backlog in the IT department, so it is helpful to use these phasesPhase 1: Preliminary Investigation pg 359The preliminary investigation is usually initiated by an end user or manager who wants a system to do something it doesnt currently do.The text introduces an fictitiou

9、s organization called “Advantage Advertising” to introduce system life cycle conceptsThree key tasks to complete during the preliminary investigation phase include:Briefly defining the problemSuggesting alternative solutionsPreparing a short reportAfter presenting the report, the managers must make

10、a decision on how best to proceed with the system changes. They canAsk for more informationKill the projectTable the project: put it on hold for a later dateMove forward with the projectNote: these decisions will be made at the end of each phase in the systems life cycleDefining the ProblemStart by

11、examining whatever current information system is in useUse interviews and observations to determine what information is needed, by whom, when, and whyAn example is given for Advantage Advertising indicating that they have problems with their manual billing systemSuggesting Alternative SystemsSimply

12、suggest some possible plans as alternatives to the present systemIt is not to evaluate whether these will completely solve the problem in the best wayExamples might include hiring more secretaries, use an existing system for sharing information, or buying a new software packagePreparing a Short Repo

13、rtSummary the results of the preliminary investigation, and suggest some alternative systemsManagement decides what to do with the project after reviewing the report. They can:Ask for more informationKill the projectTable the project: put it on hold for a later dateMove forward with the projectNote:

14、 these decisions will be made at the end of each phase in the systems life cyclePhase 2: Analysis pg 362In the analysis phase, the present system is studied in depth, and new requirements are specifiedWe are NOT concerned with the new design here, only in determining the requirements for the new sys

15、temGathering DataData is obtained by using interviews, observations, questionnaires, and studying documentsAn organization chart is one such document, which shows the relationships of employees with their levels of authority and responsibilityAnalyzing the DataThe idea is to learn how information cu

16、rrently flows, and to pinpoint why it isnt flowing appropriatelyMany tools are available including:ChecklistsA list of questions about key system issuesFor example, “can reports be easily prepared from files and documents currently in use?”Top down analysis methodStart with top level components, and

17、 break them down into smaller componentsGrid chartsShows the relationship between input and output documentsA checkmark at the intersection of a row (forms input) and column (reports output) means the input is used to create the outputDecision tablesShows the decision rules that apply when certain c

18、onditions occurFor example, if a project is less than $10,000, and the customer has a good credit history, the firm will accept the project without requiring a depositSystem flowchartsShow the flow of input data to processing and finally to outputIt does not have to be a computerized system it can s

19、how a manual processData flow diagramsShow the data or information flow within an information systemTypical symbols include those for entities, processes, files, and data flowsAutomated design toolsSoftware packages that evaluate hardware & software alternatives according to the requirements input b

20、y the system analystsComputer Aided Software Engineering (CASE) are automated design tools that help to manage the system analysis and development processDocumenting Systems AnalysisThe systems analysis report describes the:Current information system,The requirements for a new system, and aPossible

21、development scheduleManagement will then review this report and decide what action to take before the next phase #3 System DesignPhase 3: Design pg 366In the systems design phase, a new or alternative information system is designedIt consists of three tasks:Designing Alternative SystemsIn almost all

22、 instances, more than one design can be developed to meet the information needs.Each alternative must be checked for feasibility including:Economic feasibilityWill the costs of the new system be justified by the benefitsHow long will it take to pay for itselfTechnical feasibilityAre reliable hardwar

23、e, software, and training available to make the system work, and if not, can it be obtained?Operational feasibilityCan the system actually be made to operate in the organization, or will people employees, managers, clients resist it?Selecting the Best SystemManagement must consider four key question

24、s when selecting the best (optimal) systemWill the system fit in the organizations overall information system?Will the system be flexible enough so it can be modified in the future?Can it be made secure against unauthorized use?Are the benefits worth the costs?Writing the systems design reportThe sy

25、stems design report is prepared for higher management and describes alternate designs.It presents the costs and benefits and outlines the effect of alternate designs on the organizationIt concludes by recommending one of the systemsPhase 4: Development pg 368In the systems development phase, softwar

26、e and hardware are acquired and testedThis phase has three key steps:Acquiring SoftwareSoftware can be acquired two ways:Purchase it e.g. buying off the shelf software, orCustom design it e.g. build it yourself or have someone else build it (write the programs, etc.)Acquiring HardwareA system may or

27、 may not require new hardwareSwitching or upgrading hardware can be a tremendously expensive propositionTesting the New SystemAfter the software and equipment have been installed, the system needs final testing.Sample data is fed into the system, and results analyzedPhase 5: Implementation pg 369In

28、the systems implementation phase, the new information system is installed and people are trained to use it.Another name for system implementation is a system conversionThere are four primary techniques to convert to a new systemTypes of ConversionDirect approachConversion is done by abandoning the o

29、ld system and starting with the newIt is a very risky way to do things, and typically only used if it is the only alternativeParallel approachThe old and new system are run side by side until the new one is proved to be reliableIts a low risk approach to conversionIt is expensive to keep both system

30、s runningPilot approachThe new system is tried out in only one part of the organizationOnce it works smoothly in the pilot, it is rolled out to the rest of the organizationIts lower cost than the parallel approach, but has more risk (especially for the pilot part of the organization)Phased approachT

31、he new system is implemented gradually over a period of timeThe entire process is broken down into steps, and once the first step works, the next is addedIt is an expensive proposition, but low riskIn general, the pilot and phased approaches are preferred for their balance of cost and risk.Pilot wor

32、ks best when many different people do similar tasks in different locations (e.g. post office operations)Phased works best when people are doing different operationsTrainingTraining is very important, but often overlookedOne option is to begin training before the entire system is complete, so the use

33、rs are used to working with it.Phase 6: Maintenance pg 371Maintenance has two parts: a system audit and a periodic evaluation.Most organizations spend more time and money on this phase than any othersIn the system audit, the systems performance is compared to the original specifications. If the new

34、procedures are not improving productivity, some redesign may be necessaryAll systems should be evaluated from time to time to determine if they are performing as they shouldPrototyping and Rapid Applications Development pg 372Two alternate approaches requiring less time to develop systems include pr

35、ototyping and rapid application development (RAD)PrototypingPrototyping means to build a model or prototype that can be modified before the actual system is installed.Users try out the model and offer suggestions to improve itThis process is repeated until a viable system is developedIt typically ta

36、kes less time to develop systems this wayRapid Applications Development (RAD)RAD involves the use of:Powerful development software, Small specialized teams ofHighly trained personnelTo develop the system in less time that a traditional approachPaying for these resources may cost more, but the system

37、 is developed fasterUsing IT At DVD Direct A Case Study pg 373Systems Analysis and Design at DVD DirectThis section briefly describes DVD Direct, a fictitious organization, to demonstrate how systems are developed by a business.In the case, customers are switching from DVDs delivered by mail to want

38、ing them delivered over the InternetDVD Direct hopes to use streaming video to satisfy this need, and is developing a system to adapted to this new business modelUse the Computing Essentials CD to follow this caseA Look to the Future pg 374Rapid ChangeMost observers firmly believe that the pace of b

39、usiness is now faster than ever beforeTo stay competitive, businesses must integrate new technologies into their existing way of doing businessDrapkin Technology is a company that specializes in helping other companies to speed up the system development process. The company provides project assessme

40、nt, analysis, design, development, implementation, and administration.More and more companies are expected to utilize services like this in the futureVisual Summary at a glance Systems Analysis and Design pg 376System Analysis and DesignPhase 1: Preliminary InvestigationDefining the problemSuggestin

41、g Alternative SystemsPreparing a Short ReportPhase 2: AnalysisGathering DataAnalyzing the DataDocumenting Systems AnalysisPhase 3: DesignDesigning Alternative SystemsEconomic feasibilityTechnical feasibilityOperational feasibilitySelecting the Best SystemWriting the Systems Design ReportPhase 4: Dev

42、elopmentAcquiring SoftwareAcquiring HardwareTesting the New SystemPhase 5: ImplementationTypes of ConversionTrainingPhase 6: MaintenanceSystems AuditPeriodic EvaluationPrototyping and RADPrototypingRapid Applications DevelopmentKey Terms pg 3181automated design tool365software used to verify a syste

43、m designs requirements, e.g. CASE tools2checklist363set of questions a systems analyst can use to collect information about a system3computer-aided software engineering toolsCASE365software package used to design a computer system4conversion369aka system implementation - changing from an old system

44、to a new one5data flow diagram365design tool used to describe how data flows through a computer system6decision table364design tool used to check procedures that should be done depending on conditions7direct approach369implementation phase in which you abandon the old to convert to the new8economic

45、feasibility367checking if the benefits of a new system outweigh the costs9grid chart364design tool that matches the inputs to a system with the outputs10operational feasibility367checking if a new system will fit with the current systems in an organization11organization chart362analysis tool showing

46、 the working relationships of all the employees in an organization12parallel approach370implementation phase in which you run both the old and new system until you are sure the new one works13phased approach370implementation phase in which you roll out the new system in steps14pilot approach370imple

47、mentation phase in which you test out a version of the system in one location, roll it out to others later15preliminary investigation 359first step in the system life cycle in which you set goals and needs for the new system16prototyping373creating a model of the new system which is tested and revis

48、ed until you have a workable system17rapid applications developmentRAD373technique used to speed up the system life cycle process for creating a new system18system 358a collection of activities and elements organized to accomplish a goal19system flowchart364design tool used to show the relationship

49、of programs, data stores, inputs, outputs and data flows in a system20systems analysis362phase in the system life cycle in which you collect data about the current system and plan requirements for new one21systems analysis report366final report from the analysis phase showing the current system, req

50、uirements for new, and possible development schedule22systems analyst358person responsible for analyzing and planning systems for an organization23systems audit372comparing the new systems performance to the requirements set at the beginning of the design process24systems design366phase in the syste

51、m life cycle in which you plan out alternatives for building a new system25systems design report367final report from the design phase prepared for top management describing system alternatives and recommending one26systems development368phase in the system life cycle in which you acquire the needed

52、hardware, software, and system components to build it27systems implementation369phase in the system life cycle in which you train users and roll out the new system for production use28systems life cycle358a phased approach to building and modifying an organizations computer systems29systems maintena

53、nce371final phase in the system life cycle in which you make modifications to enhance the systems performance30technical feasibility367checking to see if you can acquire the proper hardware, software, and people skills to build the system31top-down analysis method363breaking a system into top level

54、modules, and breaking each of these down in turn to help build the systemChapter Review pg 319CrosswordAcross1PROTOTYPINGPG 3736OPERATIONALPG 3677RADPG 37313LIFE CYCLE (note: text has extra boxes for this word)PG 35816ORGANIZATIONPG 36217AUDITPG 37218SYSTEMPG 35819PHASEDPG 37020DECISION TABLEPG 364D

55、own1PILOTPG 3702SYSTEMS ANALYSISPG 3623PARALLELPG 3704CONVERSIONPG 3695SYSTEM DESIGNPG 3668DATA FLOW DIAGRAMPG 3659GRID CHARTPG 36410SYSTEMS ANALYSTPG 35811FLOWCHARTPG 36412TECHNICALPG 36714CASEPG 36515ECONOMICPG 367Multiple Choice1BSystems life cyclePg 3582DSystems analystPg 3583EPreliminary invest

56、igationPg 3594APreliminary investigationPg 3605BAnalysisPg 3626DCASE toolsPg 3657ASystems analysis reportPg 3668BOrganization chartPg 3639CTechnical feasibilityPg 36710BDirect approachPg 369MatchingTERMMATCHNUMBERHINTPAGEsystemN1Collection of activities and elements designed to accomplish a goal358s

57、ystems analysis & designO2A six-phase problem-solving procedure for examining and improving an information system358systems analystQ3Computer professional who studies an organizations systems to determine what actions to take and how to use computer technology to assist them358preliminary investigat

58、ionK4The first phase of the systems life cycle359systems analysisP5Data is collected about the present system362organization chartI6A chart showing management levels and formal lines of authority362checklistB7A helpful record of questions that guides the systems analyst and end user through key issu

59、es for the present system363grid chartG8Shows the relationship between input and output documents364decision tableD9Table showing the decision rules that apply when certain conditions occur364data flow diagramC10Shows the data or information flow within an information system365automated design tools

60、A11Software package that evaluates hardware and software alternatives according to requirements given by the systems analyst365economic feasibilityF12Condition in which costs of designing a new system will be justified by the benefits it will provide367operational feasibilityH13Condition in which th