Chapter3FormulationofIssues12007SYSTEMSENGINEERING1INTRODUCTIONItisveryimportant,webelieve,thattextsonsystemsengineeringandproblemsolving,ingeneral,paysignificantattentiontoissueformulation,asastepinsystemsengineeringthatneedstooccurineachofthephasesofeffort.Thisissobecause,inpractice,theresultsofapoorissueformulationeffortmaybesubjecttoverydetailedanalysis,andtheresultsofthisarecarriedoverintoimplementation.Asaresult,weobtainthewrongsystem!Needlesstosay,thisusuallyresultsinawasteofresourcesand(throughengineering)aninferiorsystem,comparedtothatwhichmighthaveresultedfromabetterissueformulation.

Issueformulationiscriticalacrossthedefinition,development,anddeploymentphasesofasystemsengineeringlifecycle.Thisisnotastepimplementedonlyaspartofthesystemsdefinitionphase,althoughitisveryimportantinthatphase.3/10/202322007SYSTEMSENGINEERING1INTRODUCTIONAproblem,oranissueasagenerallysynonymousterm,canusuallybeviewedfromseveralperspectives,andthesolutionthatresultswilloftenbeastrongfunctionoftheperspectivesfromwhichaproblemisviewedandformulated.3/10/202332007SYSTEMSENGINEERING2SITUATIONASSESSMENTCompletesituationassessmentconsistsofthreebasicstepsthatareintendedtoanswerthethreequestionshighlightedinFigure3.1.3/10/202352007SYSTEMSENGINEERING2SITUATIONASSESSMENTThefirstpartistheidentificationofthe(immediate)pastintermsofthequestion,Whatwas?

Thesecondpartofasituationassessmentexaminesthecurrentstatusorpositionofthingsrelativetothegoal.Itisadescriptivecomponentandanswersthequestion,Whatis?Thethirdornormativecomponentofasituationassessmentanswersthequestion,Whatoughttobe?

Understandingofthemajor,ideallyall,factorsinfluencingthepast,present,andfutureisneededforagoodsituationassessment.Thereisahorizoncomponentofsituationassessmentanditanswersthequestion,Whatfactorsovertimematterandwhendotheymatter?

3/10/202362007SYSTEMSENGINEERING2SITUATIONASSESSMENTWehaveacompletesituationassessmentonceweknowthefollowing:Whatdowewanttoaccomplish?Whatisthepastandcurrentstateofaffairsrelativetoourgoalbroughtaboutbythechangedsituation?Whataretherelevantfactorsthatinfluencethesituationandtheirassociatedtimeframe.3/10/202372007SYSTEMSENGINEERING2SITUATIONASSESSMENT

Accomplishingahigh-qualitysituationassessmentdependsonseveralfactors.First,theexperientialfamiliaritywiththeissuesorproblemunderconsiderationisveryimportant.

Forexample,itisunlikelythatsomeonewithverylittlebackgroundknowledgeaboutnuclearpowerplantswouldbeable,withoutconsiderablestudy,todevelopusefulalternativesforensuringsafeoperationofsuchafacility.Aswehavealreadynoted,knowledgeisinformationinarelevantcontext.3/10/202392007SYSTEMSENGINEERING2SITUATIONASSESSMENT

Butyouneedmorethanjustknowledgeaboutthespecificproblemorissueathand.Familiaritywiththeenvironmentintowhichthespecificissueorproblemisembeddedisalsocrucialtoanunderstandingofcontext.

Forexample,thedesignofasuccessfulinformationsystemforairlinereservationagentsismademucheasierbysomeonewithanindepthknowledgeofthevarioustasksthatsuchagentsperformandtheenvironmentthatagentsmustcopewithastheyperformthesetasks.Youcouldlearnalotaboutdesigningsuchasystemfromsomeonewhoisanexpertatdevelopinghuman-computerinterfaces.Butyoucanalsoappreciatehowhelpfulitwouldbetointerviewsomeexperiencedticketagentsandtofindoutaboutthedifficultiestheyexperiencewhentalkingtocustomersandbookingtheirflights.

Itisthejobofsystemsengineerstomakesurethattherelevantknowledgeofexperiencedpeopleisbroughtintoaprojectandusedinissueformulation.Capturingthisknowledgeoftenrequiresthesystemsengineertoskillfullyconductbothindividualinterviewsandgroupmeetings.

3/10/2023102007SYSTEMSENGINEERING2SITUATIONASSESSMENT

Anormativescenariodescribeshowthestakeholderswantthesystemtobeinthefuture.

Thisisnotaseasytoaccomplishasitmightappeartobe.Wewilloftenneedtodistinguishbetweenrealisticneedsandfrivolouswants.Oftenalso,importantstakeholdershaveconflictingopinionsonwhatthefutureshouldbe,oronb.Somehaveunrealisticexpectationsofwhattechnologycandeliverinthetimeframe（期限）underconsideration.Othersarereluctanttoseeanychangesbecausetheythinktheirjoborrelationshiptoasystemmaybeputinjeopardy（危險）.Askilledsystemsengineermustbrokerthesevariousintereststocreateenthusiasmandsupportforatechnicallyfeasible,trustworthyproject.Onewayofgainingsupportforanimprovementtoanexistingsystemorforacompletelynewsystemistoinvolvestakeholdersintheprocess.Helpingpeoplevisualizethefutureinmeaningfulwayswillgoalongwaytowardcreatingausefulnormativescenario.3/10/2023112007SYSTEMSENGINEERING2SITUATIONASSESSMENT

Ifthereisnotacurrentsystemtoobserve,thenyouneedtocreateawayofseeinghowanentirelynewsystemmightwork.Anumberofusefulwaysexistforthis.Agroupofpeoplewithrelevantknowledgecanmeetandtalkthroughhowanewsystemmightwork.

3/10/2023132007SYSTEMSENGINEERING2SITUATIONASSESSMENTManyotherwaysexistforexaminingpossibilitiesfornewsystems.Prototypes[3,4]canbebuiltandpotentialuserscanexperimentwiththemthroughsimulation.Aprototypeisafirst-cutapproximationofwhatanewsystemmightbe.Thepurposeofaprototypeistoquicklygaininformationfromtheuseraboutwhatseemstoworkandwhatisneeded.

Forexample,aprototypeofanewinformationsystemmightbeasetofscreensthatausercouldviewandcommentastohowusefulthescreensareinhelpingprovideneededinformation.3/10/2023142007SYSTEMSENGINEERING2SITUATIONASSESSMENT

Amodelofthesituation,andtheresultingsimulationofoperationsusingthemodel,canemulatetheoperationofanewsystem.Tobuildasimulationrequiresamodelorsomerepresentationofthenewsystem.Theusualpurposeofasimulationistogetanideaofhowthenewsystemmightactuallyworkifitwereputintooperation.

Forexample,acitywantingtobuildanairportatanewlocationmightliketoknowifthelandavailablecanaccommodatethenumberofplanesthattheyanticipatewillbelandingandtaking-offfromtheirnewfacility.Asimulationofanairportthatfitswithinthecity'slandconstraintcanbetestedtoseeifanyairportlayoutscansuccessfullymeetanticipatedpassengerandfreightdemands.

3/10/2023152007SYSTEMSENGINEERING3APPROACHESTOSITUATIONASSESSMENT

Thenotionofathresholdisoftenveryimportantinsituationassessment.

Wemighthaveathresholdforasituation,andobservingthisthresholdmightbeallthatisrequired.Whenthesituationdescriptorvaluesexceedthisthreshold,wemightthendecidetoassessitingreaterdetail.Ifitisbenign,wemaychoosetoignoreit;ifitisnotbenign,wemaydecidetoreacttoitorcontinuetoobserveit.

Areasonablygoodillustrationofthisisthesituationassessmentoftemperatureofthehumanbody.Oneofthepotentialdifficultiesrelativetoobservingasituationisthatwewishtobeabletointeractivelyandproactivelydealwithissuesandnotsimplytoreacttodifficultiesaftertheyhaveeventuated.3/10/2023172007SYSTEMSENGINEERING3APPROACHESTOSITUATIONASSESSMENT

Thegeneralsituationassessmentprocess,illustratedinFigure3.2,bedescribedbythefollowingeightsteps:Wemakegeneralobservationsofasmanypertinent（有關的）aspectsofthesituationaroundusasispossibleinordertoidentifyorconfirmthedescriptivescenarioorstatusquo（現(xiàn)狀）.Weseeifthisinformationindicatesachangeinthecurrentsituation.Ifthereisnochange,wegobacktostep1.Ifthereisachange,weproceedtostep3.Weidentifyorformulateanumberofalternativehypothesesthatmaydescribethenewsituation,ordescriptivescenario.Weattempttodetermineifanymoreinformationinputsarerequiredfordecidingwhichalternativehypothesisisthemostlikelyone.3/10/2023182007SYSTEMSENGINEERING3APPROACHESTOSITUATIONASSESSMENT

Weobtaintherequiredinformationfromsuchinputsourcesasaprioripredefinedstoredinformation,humanobservations,humanknowledge,orsensormeasurements.Weprocessthisinformationandknowledgetoconfirmordisconfirmeachofthealternativehypotheses.Weidentifythehypotheseswiththehighestprobability(ies)ofbeingtrueandidentifytheassociatedsituationassessmentwithsomeappropriatequantificationofourconfidenceintheassessment.Wedetermineiftheassessmentconfidencefordescribingthesituationissufficientlyhigh.Ifitisnot,wegobacktostep3or4andrepeattheassessmentprocessuntiltheconfidencethresholdisachieved.Whenitis,wehaveassessedthesituationandwegoonwiththerestoftheproblem-solvingorissueformulationprocess.3/10/2023192007SYSTEMSENGINEERING3APPROACHESTOSITUATIONASSESSMENT

Oneofthemostdifficultproblemsincomplexdecisionsituationsisgatheringtheappropriateinformationandproperlyassessingthesituation.MasonandMitroffareamongthemanywhohavecommentedonthisreality.Theseauthorsidentifythreetypesoferrorsthatcanoccurinassessingasituation:TypeIerrorsareerrorsthatresultfromincorrectlyassessingthatthereisaproblemwhenthereisnoproblem.TypeIIerrorsareerrorsthatresultfromincorrectlyassessingthatthereisnoproblemwhenthereisaproblem.TypeIIIerrorsareerrorsthatresultfromcorrectlyassessingthatthereisaproblem,butincorrectlyidentifyingthenatureoftheproblem.3/10/2023212007SYSTEMSENGINEERING3APPROACHESTOSITUATIONASSESSMENT

TypeIerrorsaregenerallycalledfalsealarms;TypeIIerrorsarecalledmissesormissedproblemerrors;TypeIIIerrorscannotgenerallybeovercomebyeventhebestmethodsofproblemsolvingbecauseoneissolvingtheincorrectproblem.Onlybysomerarefortuitous(幸運)circumstancewouldoneeverendupwithanappropriatesolutionfortherealproblemathandaftermisdiagnosisandimplementingacourseofactionforthewrongproblem.AmajorreasonforsituationassessmentistoavoidTypeIIIerrors.3/10/2023222007SYSTEMSENGINEERING3APPROACHESTOSITUATIONASSESSMENT

TypeIIIerrorsoccurmostfrequentlywhenproblemsareill-structured.Inthiscontext,itislikelythatthemostdifficultstepinthedecisionprocesswouldbetheproblemdefinitionorsituationassessment.ComplexproblemsarethoseproblemsthatrequiremultidisciplinaryperspectivesifTypeIIIerrorsaretobeminimized.Aproblemisill-structuredwhenoneormoreofthedecisionalternatives,decisionoutcomes,valuesorweightsofimportanceoftheoutcomes,ortheprobabilitiesofthevariousoutcomesthatresultfromimplementingvariousalternativecoursesofactionareeitherunknown,impreciselyknown,oruncertain.3/10/2023232007SYSTEMSENGINEERING4PROBLEMORISSUEIDENTIFICATION

Thetoughestpartofmostsystemsengineeringeffortsisidentifyingtheproblemcorrectly.Manyengineeringefforts,althoughtheymayrepresentgreatfeatsofengineeringskill,failbecausetheyweredesignedtosolvethewrongproblemorbecausetheimplementedsolutioncreatedmoreproblems.3/10/2023252007SYSTEMSENGINEERING3PROBLEMORISSUEIDENTIFICATION

Forexample,considertheAswanDaminEgyptbuiltinthe1960s.HundredsoftheSovietengineerssetaboutandsuccessfullybuiltoneofthebiggestdamsandhydroelectricalfacilitiesintheworld.However,astheEgyptianssoonfoundout,theeffortwas,inmanyrespects,agrandfailurebecauseitdestroyedmuchoftheprecious（寶貴的）,arable（可耕種的）landintheNileRiverValley.TheNileRiver‘snaturalfloodingprocesshadcontinuallyreplenished（）thesoildownstreamandmadeitpossibleformanycropstogrowinfertileriver-bottomland.Oncethedamwasinplace,thenaturalfloodsnolongerreplenishedthelandandvastamountsofformerlyrichagriculturallandwaslostforever.Egypt,whichhadbeenabletofeeditself,soonbecamedependentonfoodexports.Furthermore,thedamfloodedforevermanypricelessancientruinsunderdeepwaterthatwereupstreamfromthemassivedam.3/10/2023262007SYSTEMSENGINEERING4.1ScopingandBoundingtheProblem

howcanyousuccessfullyidentifytherelevantquestionsanddifficultiesinalarge-scaleproject?Properlyscopingandboundingasystemsengineeringeffortistheanswer.Toscopeaprojectmeanstounderstandwhytheprojectisnecessary,whatthestakeholdersintendtoaccomplishwiththeproject,andhowtomeasureprojectsuccess.Insystemsterms,thismeansidentifyingtheneeds,objectives,andcriteriafortheproject.Theneedstellwhytheprojectisnecessary.Relatedtotheneeds,theobjectivesdescribeindetaileverythingthattheprojectisintendedtoaccomplish.Criteriameasuresuccessinachievingtheobjectives.3/10/2023292007SYSTEMSENGINEERING4.1ScopingandBoundingtheProblem

Toboundaprojectmeanstounderstandthelimitationsassociatedwiththeproject,thechangesthatcanbemadetoachievedesiredobjectives,andtheimportantquantitiesthatarelikelytochangeasaresultoftheproject.

Insystemsterms,thismeansidentifyingtheconstraints,parameters,andvariablesfortheproject.Constraintsarethelimitsthatmustbeobservedfortheproject.Constraintsincluderealisticconsiderationsrelatedtothingssuchasmoney,time,people,organizations,andsociety.Forexample,mostprojectshavebudget,timedeadlines,andenvironmentalimpactconstraints.3/10/2023302007SYSTEMSENGINEERING4.1ScopingandBoundingtheProblem

Parametersarefactorsthatdefineanalternativeanddetermineitsbehavior.Thevaluetowhichparametersaresetrestrictwhatresultsarepossibletoachievewithanalternative.

Forexample,inthedesignofamasstransitsystemforacity,someparametersmightbethenumberofbusesandtrains.Howmanypeoplecanbemovedbyanyspecificmasstransitalternativedependsonthevaluetowhichtheseparametersareset—howmanybusesandtrainsthereareforanalternative.Onceasystemisinoperation,parametersdonotchangemuch.Everydaythatthecityoperatesthemasstransitsystem,thesamenumberofbusesandtrainsarepartofthesystem.Parametersarefactorsthatthesystemsengineermanipulatestocreatealternativesandaltertheirperformance.Todistinguishparametersfromthequantitiesassociatedwithmathematicalmodels,youcanrefertothemasalterables.3/10/2023312007SYSTEMSENGINEERING4.1ScopingandBoundingtheProblem

Incontrasttoparameters,responsevariablesarelikelytochangeoncethesystemisinoperation.Variablesaremeasurablequantitiesthatyouwanttomonitorasthesystemoperates.Forexample,thenumberofpassengersthatusethebusesortrainseachdayisaresponsevariablethatchangesasthesystemoperates.

Forlarge-scalesystemsthenumberofsuchvariablescanbeoverwhelming.Thatiswhyweusetheconceptofstatevariables.3/10/2023322007SYSTEMSENGINEERING4.2SystemsDefinitionMatrix

Statevariablesareacollectionofresponsevariablesthatwechoosetomonitortoinformusaboutthestatusofasystem.Thespecificvariableschosendependonwhywewanttheinformation.

Ifwearesystemengineersinvestigatingtheadequacyofacurrentlyexistingmasstransitsystem,thenweprobablywanttoknowanumberofvariablesatdifferenttimesofthedayandweek.Forexample,twostatevariablesmightbethenumberofpassengersperrouteandthenumberofoperationalbusesandtrains.3/10/2023332007SYSTEMSENGINEERING4.2SystemsDefinitionMatrix

AconvenientwayforthesystemsengineertodocumentthescopingandboundingofaproblemistouseasystemsdefinitionmatrixliketheoneshowninFigure3.4.Thematrixhastwomainsections.Onesectiondefinesthescopeoftheprojectbylistingtheneeds,objectives,andcriteria.Theothersectionliststheparameters,variables,andconstraintsanddefinestheboundsoftheproject.Thesimpleframeworkofthesystemsdefinitionmatrixisusefulasachecklistforinformationgathering,documentation,andcommunication.3/10/2023342007SYSTEMSENGINEERING4.2SystemsDefinitionMatrixThesimplematrixsuggestedherecanbeexpandedtoincludemorefeaturesandelementsofaproposedsystemorproject.

Forexample,thepurposesandbasicfunctionsofasystem,itsinputs,outputs,majorcomponents,humanagents,environment,superandlateralsystems,andinterfacesandcontrolscouldallbedimensionsofthesystemthataredescribedinthematrix.3/10/2023352007SYSTEMSENGINEERING4.2SystemsDefinitionMatrixIfyouwanttoputmoredetailsinthematrix,youcancreateasystemsdefinitionmatrixforeachsubsystemofthelargersystem.Foramultiprojectprogram,youmightwanttocompleteasystemdefinitionmatrixforeachmajorprojectintheprogram.Foramultistageproject,youmaywanttocompleteamatrixforeachphaseoftheproject.Additionally,youcanusethesematricestohelpyouidentifyandspecifytheinteractionsamongthevariouscomponents.3/10/2023362007SYSTEMSENGINEERING4.2SystemsDefinitionMatrixThesystemdefinitionmatrix,whencomplete,shouldgiveyouandthosethatyouneedtocommunicatewithathoroughpictureofthebasicingredientsofanexistingorproposedsystem.Itcanhelpyoutodiscoverinsightsintothefeasibilityandinternalconsistencyofaproposeddesign.Alsoitcanhelpyouidentifydifferentwaysthatyoucanmakeimprovementstoanexistingsystem.3/10/2023372007SYSTEMSENGINEERING4.3NeedsandConstraints:IdentificationandAnalysisBecausetheformulationofasuccessfulsystemdependsonmeetingtheeffectiveneedsofthecustomer,itisnowonderthatoftenthereisgreatimportanceplacedonidentifyingandanalyzingtheneedsforaproject.Sucheffortshavebecomesoimportantthattheyhavebeengiventheirowncategory:needsanalysis.

Whatareneedsandhowaretheyanalyzed?First,aneedisalackofsomethingdesiredorrequired.Maslow[17]definedahierarchyofneedsforpeoplethatshowshowbasiclower-levelphysicalneedssuchashungerorthirstmustbesatisfiedfirstbeforehigher-levelemotionalandmentalneedssuchasloveandself-esteembecomeimportant.3/10/2023382007SYSTEMSENGINEERING4.3NeedsandConstraints:IdentificationandAnalysisPhysiologicalneeds,suchasfood,clothing,andhealthSafetyneeds,suchasstability,security,andorderBelongingnessneeds,suchasaffectionandaffiliationEsteemneeds,suchasself-respect,prestige,andsuccessSelf-actualizationneeds,enablingrealizationofdevelopmentpotentials3/10/2023392007SYSTEMSENGINEERING4.3NeedsandConstraints:IdentificationandAnalysisSoasMaslowhasshown,needsstemfrombeinghuman.Buthumansalsodesiretoengageinmanydifferentactivities.Manyneedscomefromthedesiretoimproveorenhancehumanactivities.Peoplearealwayswantingtodothingsfaster,easier,cheaper,andbetter,insomeway.Technologyitselfisoftendefinedastheapplicationofscientificknowledgetoenhanceperformanceofsomehumanactivity.Asweknowfromtheincreasingpaceofadvancesintechnology,needsarelimitless.Butnoticethatweputtheword"effective"infrontofneedsinourdefinitionofsuccessfuldesign.3/10/2023402007SYSTEMSENGINEERING4.3NeedsandConstraints:IdentificationandAnalysisWhatisaneffectiveneed?Thisisbestansweredbywhatoneisnot.Aneffectiveneedisnotaprimitiveneed,or"want."Primitiveneedsaretheunsupportedopinionsofpeopleinvolvedwithasystem.Primitiveneedsareusuallynarrowlyfocusedassertionsorbeliefsthatpeoplehave.Theseopinionsnormallyreflecttheirpositionorrolewithinasystem.

Forexample,inanassemblyfacilitythatisexperiencingproblems,primitiveneedsfromassemblylineworkersmayfocusonmanagementexpertiseastheproblemthatmustbeaddressed.Managementmayassertthattheworkersaretheproblem.3/10/2023412007SYSTEMSENGINEERING4.3NeedsandConstraints:IdentificationandAnalysisWheredoesthetruthlie?Likeanygooddetective,thesystemengineercannotbegintosayuntiltheinvestigationhasbeenbroadenedandevidencegatheredandobjectivelyanalyzed.Thismeansthesystemsengineershouldlookbeyondjusttheimmediate,obviouscluesathand.Perhapstherearefactorsintheenvironmentoftheassemblyplantitself,beyondtheimmediatecontrolofeithertheassemblyworkersorlinemanagement,thataretheculprits（事故的原因）.Aneedsanalysiswillbroadenthesearchbeyondprimitiveneedstatementsandlookforevidencetosupportclaimsofeffectiveneeds.Forinstance,onestrongpieceofevidencethataneffectiveneedexiststobringanewsystemintobeingortoimproveanexistingsystemisthatthereissomeonewillingtopayforit!However,thepresenceofsuchawillingnesstopayisneithernecessarynorsufficienttoassureeffectivenessofaneed.Otherevidencecanbegatheredfromhistoricalaccountsorlogsofsystemperformance.3/10/2023422007SYSTEMSENGINEERING4.3NeedsandConstraints:IdentificationandAnalysisIfapreponderance(優(yōu)勢)ofthemajorstakeholdersofasystemaresayingthataneedexiststoimprovesomeaspectofasystem,thenitismorelikelythataneffectiveneedexists.

Forexample,ifpostalpatrons,maildeliverypeople,andpostmastersarealltalkingandwritingaboutanalarmingincreaseinlostandstolenmail,thenevidenceisbeginningtoindicateaneffectiveneed.Still,youwanttogatherbetterevidence.Thismeansthatcollectingandanalyzingdataareoftennecessary."Legalauthoritiesreporta25%increaseofreportedlostandstolenmailincidentsthisyear"isacompellingpieceofevidence.Thebottomlineisthateffectiveneedsmustbesupportedbyorganized,compellingevidence.Agoodsystemsengineercitesevidencelinkedwithsoundrationalewhenpresentingtheresultsofaneedsanalysis.3/10/2023432007SYSTEMSENGINEERING4.3NeedsandConstraints:IdentificationandAnalysisEffectiveneedsareneedsthatmeetthreebasicconditions.

First,theyareneedsthatcanbesupportedbyorganizedevidence.Analyzingpast,present,andfuturetrendsrelatedtothetangible（切實的）needinquestioncanhelpprovideevidence.

Forexample,marketresearchandbusinesstrends,ifproperlyfocused,canrevealimportantinsightsabouttheneedfornewproductsandservices.

3/10/2023442007SYSTEMSENGINEERING4.3NeedsandConstraints:IdentificationandAnalysisThisorganizedevidencemustinturnbetiedtoconvincingrationale.

Forexample,ifmarketresearchshowsthatpeoplearewillingtospendsomeoftheirdisposableincomeonanewentertainmentservice,thereshouldbesomecompellingrationalethatexplainswhypeoplewouldwanttospendtheirmoneyforthisnewserviceinsteadofsomeotherleisurepursuitorexistingentertainmentsystem.Thisleadstothenextcondition,whichstipulatesthatsomeonemustbewillingtopayforit!

Thereisnotmuchreasontoconsidergreatplansfordesigninganewsystemorstartingalargeimprovementprojectifnoonecanraisethefundstopayforthem.3/10/2023452007SYSTEMSENGINEERING4.3NeedsandConstraints:IdentificationandAnalysis

Thelastconditionsimplysaysthateffectiveneedsmustbeneedsthatcanactuallybecarriedoutorsatisfied.

Nomatterhowmuchevidencewecompileorhowmuchmoneyweraise,therearesomeneedsthatarebeyondthehumangraspor,atleast,arebeyondtherealmofwhatiscurrentlypossible.Manyschemesthatplayonthehopesandfearsofpeopleandattractmuchattentionandmoneydonotmeetthislastcondition.Thesystemsengineermusthavetheintegrityandobjectivesoundjudgmenttoidentifyfutile（無用的）projectsthatwillonlywastescarce（稀有的）resources.3/10/2023462007SYSTEMSENGINEERING4.4Input-OutputMatrix

averyusefuldeviceforthinkingabouttheneedsandconstraintsforaproposedsystemisabasicsysteminput-outputmodel.Thefamiliarsysteminput-outputmodelappearsasshowninFigure3.5.Ostrofskyshowshowtocreateaninput-outputmatrixthatexaminesdifferenttypesofinputsandoutputsoverthesystem'stotallifecycle.Constructingoneoftheseinput-outputmatricesisfairlysimpleasshowninFigure3.6.3/10/2023472007SYSTEMSENGINEERING4.4Input-OutputMatrix

Youdividetheinputsintotwothought-provoking（發(fā)人深省的）categories,intendedandenvironmental.

Intendedinputsareonesthatthesystem'sdesignersandoperatorscancompletelydetermineorcontrol.Thisincludesthingssuchasfacilities,resources,procedures,organizationalstructure,andrawmaterials.Environmentalinputsareinputsthatmayoccurbutoftencannotbecontrolled.However,itmaybepossibletopartiallycontrol,influence,ormitigatetheeffectsofenvironmentalinputs.Someexamplesareweather,customerdemand,laborrelations,andgovernmentregulations.3/10/2023482007SYSTEMSENGI