Bài giảng Phân tích hệ thống

rmation SystemsProcess of returning to the beginning of the SDLC and repeating development steps focusing on system change until the change is implementedFour major activities1.	Obtaining maintenance requests2.	Transforming requests into changes3.	Designing changes4.	Implementing [email protected]@utt.frDeliverablesDevelopment of a new version of the software, new versions of all design documents and training materials created or modified during the maintenance [email protected] Application TestingA test plan is developed during the analysis phaseDuring the design phase, a unit test plan and a system test plan are developedThe actual testing is done during implementationTest plans provide improved communication among all parties involved in testingServe as [email protected] of TestingInspectionA testing technique in which participants examine program code for predictable language-specific errorsWalkthroughA peer group review of any product created during the systems development process; also called a structured walkthroughDesk CheckingA testing technique in which the program code is sequentially executed manually by the [email protected] of TestingUnit TestingEach module is tested alone in an attempt to discover any errors in its code, also called module testingIntegration TestingThe process of bringing together all of the modules that a program comprises for testing purposes. Modules are typically integrated in a top-down, incremental [email protected] of TestingSystem TestingThe bringing together of all the programs that a system comprises for testing purposes. Programs are typically integrated in a top-down, incremental fashionStub TestingA technique used in testing, especially where modules are written and tested in a top-down fashion, where a few lines of code are used to substitute for subordinate [email protected] Testing ProcessThe purpose of the testing is confirming that the system satisfies requirementsTesting must be plannedTest CaseA specific scenario of transactions, queries or navigation paths that represent a typical, critical or abnormal use of the systemTest cases and results should be thoroughly documented so they can be repeated for each revision of an [email protected]@utt.frAcceptance Testing by UsersThe process whereby actual users test a completed information system, the end result of which is the users’ acceptance of [email protected] Testing by UsersAlpha TestingUser testing of a completed information system using simulated dataRecovery testingForces the software (or environment) to fail in order to verify that recovery is properly performedSecurity testingVerifies that protection mechanisms built into the system will protect it from improper penetrationStress testingTries to break the systemPerformance testingDetermines how the system performs on the range of possible environments in which it may be [email protected] Testing by UsersBeta TestingUser testing of a completed information system using real data in the real user [email protected] organizational process of changing over from the current information system to a new oneFour approachesDirect InstallationChanging over from the old information system to a new one by turning off the old system when the new one is turned onParallel InstallationRunning the old information system and the new one at the same time until management decides the old system can be turned [email protected] location installationTrying out an information system at one site and using the experience to decide if and how the new system should be deployed throughout the organizationPhased InstallationChanging from the old information system to the new one incrementally, starting with one or a few functional components and then gradually extending the installation to cover the whole new [email protected]@utt.frPlanning InstallationConsiderationsData conversionError correctionLoading from current systemPlanned system shutdownBusiness cycle of [email protected] the SystemSystem documentationDetailed information about a system’s design specifications, its internal workings and its functionalityInternal documentationSystem documentation that is part of the program source code or is generated at compile timeExternal documentationSystem documentation that includes the outcome of structured diagramming techniques such as data flow and entity relationship [email protected] the SystemUser DocumentationWritten or other visual information about an application system, how it works, and how to use itPreparing user documentationTraditional source has been information systems departmentApplication-oriented documentation is now often supplied by vendors and users [email protected] Information System UsersPotential training topicsUse of the systemGeneral computer conceptsInformation system conceptsOrganizational conceptsSystem managementSystem [email protected] Information System UsersTraining methodsResident expertComputer-aided instructionFormal coursesSoftware help componentsTutorialsInteractive training manualsExternal sources, such as [email protected]@utt.frTraining Information System UsersElectronic performance support system (EPSS)Component of a software package or application in which training and educational information is [email protected] Information System UsersSupport is extremely important to usersJ.D. Power and Associates survey found user support to be number one criterion contributing to user satisfaction with personal computingMost organizations provide support by two meansInformation centerHelp [email protected] Information System Users:Information CenterAn organizational unit whose mission is to support users in exploiting information technologyStaff might perform the following tasksInstall new hardware or software and set up user accountsConsult with users writing programs in fourth-generation languagesExtract data from organizational databases onto personal computersAnswer basic on-demand questionsProvide a demonstration site for viewing hardware and softwareWork with users to submit system change [email protected] Information System Users:Help DeskA single point of contact for all user inquiries and problems about a particular information system or for all users in a particular [email protected] Implementation Sometimes FailsTwo conditions necessary for a successful implementationManagement support of the system under developmentInvolvement of users in the development [email protected] Implementation Sometimes FailsInsights about implementation processRiskCommitment to the projectCommitment to changeExtent of project definition and planningRealistic user expectationsImplementation success factorsExtent to which system is usedUser’s satisfaction with [email protected] Close DownEvaluate teamReassign members to other projectsNotify all affected parties that the development project is ending and that you are switching to operation and maintenance modeConduct post-project reviewsClose out customer contractFormal [email protected] System MaintenanceCorrective maintenanceChanges made to a system to repair flaws in its design, coding, or implementationAdaptive maintenanceChanges made to a system to evolve its functionality to changing business needs or technologiesPerfective maintenanceChanges made to a system to add new features or to improve performancePreventive maintenanceChanges made to a system to avoid possible future [email protected] System Maintenance:The Cost of MaintenanceMany organizations allocate eighty percent of information systems budget to maintenanceFactors that influence system maintainabilityLatent defectsNumber of customers for a given systemQuality of system documentationMaintenance personnelToolsWell-structured [email protected] System Maintenance:Measures of EffectivenessNumber of failuresTime between each failureType of failureMean time between failures (MTBF)A measurement of error occurrences that can be tracked over time to indicate the quality of a [email protected] Maintenance RequestsDetermine type of requestErrorAdaptationEnhancementFigure 10-9 shows a flowchart for a request [email protected]@utt.frConfiguration ManagementThe process of assuring that only authorized changes are made to the systemBaseline modulesSoftware modules that have been tested, documented, and approved to be included in the most recently created version of a systemSystem librarianA person responsible for controlling the checking out and checking in of baseline modules when a system is being developed or maintainedBuild routinesGuidelines that list the instructions to construct an executable system from the baseline source [email protected] of coding, testing and converting an organizational information systemFour installation strategiesDirectParallelSingle locationPhased installation368myriam.lewkowicz@utt.frSummaryDocumentationSystemUserUser trainingProviding support for end usersSystems implementation failures369myriam.lewkowicz@utt.frSummaryMaintenanceCorrectiveAdaptivePerfectivePreventiveCost of maintenanceMeasuring effectiveness of [email protected] maintenance requestsConfiguration managementInternet [email protected]