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 changes334myriam.lewkowicz@utt.fr335myriam.lewkowicz@utt.frDeliverablesDevelopment of a new version of the software, new versions of all design documents and training materials created or modified during the maintenance effort336myriam.lewkowicz@utt.frSoftware 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 checklists337myriam.lewkowicz@utt.frTypes 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 reviewer338myriam.lewkowicz@utt.frTypes 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 fashion339myriam.lewkowicz@utt.frTypes 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 modules340myriam.lewkowicz@utt.frThe 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 application341myriam.lewkowicz@utt.fr342myriam.lewkowicz@utt.frAcceptance Testing by UsersThe process whereby actual users test a completed information system, the end result of which is the users’ acceptance of it343myriam.lewkowicz@utt.frAcceptance 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 used344myriam.lewkowicz@utt.frAcceptance Testing by UsersBeta TestingUser testing of a completed information system using real data in the real user environment345myriam.lewkowicz@utt.frInstallationThe 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 off346myriam.lewkowicz@utt.frInstallationSingle 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 system347myriam.lewkowicz@utt.fr348myriam.lewkowicz@utt.frPlanning InstallationConsiderationsData conversionError correctionLoading from current systemPlanned system shutdownBusiness cycle of organization349myriam.lewkowicz@utt.frDocumenting 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 diagrams350myriam.lewkowicz@utt.frDocumenting 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 themselves351myriam.lewkowicz@utt.frTraining Information System UsersPotential training topicsUse of the systemGeneral computer conceptsInformation system conceptsOrganizational conceptsSystem managementSystem installation352myriam.lewkowicz@utt.frTraining Information System UsersTraining methodsResident expertComputer-aided instructionFormal coursesSoftware help componentsTutorialsInteractive training manualsExternal sources, such as vendors353myriam.lewkowicz@utt.fr354myriam.lewkowicz@utt.frTraining Information System UsersElectronic performance support system (EPSS)Component of a software package or application in which training and educational information is embedded355myriam.lewkowicz@utt.frSupporting 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 desk356myriam.lewkowicz@utt.frSupporting 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 requests357myriam.lewkowicz@utt.frSupporting 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 department358myriam.lewkowicz@utt.frWhy Implementation Sometimes FailsTwo conditions necessary for a successful implementationManagement support of the system under developmentInvolvement of users in the development process359myriam.lewkowicz@utt.frWhy 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 system360myriam.lewkowicz@utt.frProject 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 signoff361myriam.lewkowicz@utt.frConducting 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 problems362myriam.lewkowicz@utt.frConducting 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 programs363myriam.lewkowicz@utt.frConducting 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 system364myriam.lewkowicz@utt.frControlling Maintenance RequestsDetermine type of requestErrorAdaptationEnhancementFigure 10-9 shows a flowchart for a request procedure365myriam.lewkowicz@utt.fr366myriam.lewkowicz@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 code367myriam.lewkowicz@utt.frSummaryProcess 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 maintenance370myriam.lewkowicz@utt.frSummaryControlling maintenance requestsConfiguration managementInternet development371myriam.lewkowicz@utt.fr