TowardtheidealmechanicalengineeringdesignsupportsystemDavidG.UllmanAbstractThispaperdetailstheprogresstowardthedevelopmentoftheidealmechanicalengineeringdesignsupportsystem.ItattemptstolookatthegapbetweentheneedsofamechanicalengineerandwhatiscurrentlyavailableonCADsystemsSincethetern：CADemphasizesthatthecomputerisanaidtothehumandesigner，thispaperisdesignercentricitisbasedheavi~ontheactivitiesperformedbydesignersandthetypesofinformationdevelopedbythen：SeventeengoalsfortheidealmechanicaldesignsupportsystemarelistedThesearedirectedatthetypesofinformationdevelopedduringthedesignprocessandtheactivitiesusedtodevelopthemForeachoftheseventeen，backgroundinformation，thecurrentstateoftheart，andopportunitiesforfuturedevelopmentareitemizedKeywordsMechanicalengineeringdesign，CAD，Supportsystem1IntroductionThispapersummarizestheprogressmadetowardthedevelopmentoftheidealmechanicalengineeringdesignsupportsystemFornearly30years，computeraideddesign(CAD)systemshavebeentoutedbytheirdevelopersassystemsthatsupportengineeringdesignersdevelopingproductsCADsystemshavehadamajorimpactonhowdesignisaccomplishedintheworkplaceThisbeingsaid，thereisamazinglylittleibrmalresearchontheeffectsofthesesystemsonthedesignersandonthefinalproducts’ThispaperpresentsastructurefordiscussingtheseeffectsIndoingso、ltsummarizeswhatisknownandwhatneedscobestudiedFinally、itdiscusseshowCADsystemshaveevoh,edtosupportincreasingportionsoftheactivitiesthatareusedtodevelopproducts.ThetermCADemphasizesthatthecomputerlsanaidtothehumandesigner，sothispaperisdesignercentricitisbasedheavilyontheactivitiespertbrmedbydesignersandthetypesofintbrmationdevelopedbytheminmanyways，thisisanupdateoftwoearlierpapers，‘‘Theimportanceofdrawinginthemechanicaldesignprocess”[29Jand“issuescriticaltothedevelopmentofdesignhistory，designrationaleanddesignintentsystems”【311Thelatterpaperdeveloped13outstandingissuesthatneededtoberesolvedtorealizethecaptureandqueryofengineeringdesignintormationasapotentiallorlmprovmgthedesignprocessandthereuseofdesignIntormation.ThetbundationforthefirstpaperwasthestudyofthemarksmadeonpaperbynvemechanicaldesignengineersofvaryingbackgroundsandexperienceTheywereeachgiventheinitialspecificationstbroneoftwot~irlysimple，yetrealistic，mechanicaldesignproblemstakenfromprofessionalpracticeTheengineerswererequestedtothinkaloudastheysoh,edtheproblemsTheirverbalreports、drawings，andgestureswerevideoandaudiotapedforaperiodof610hThetapeddatawerethentranscribedtoobtaina‘‘protocol”ofthedesignsessionEachdesignermadenumerousdrawingsduringhisorhersolutionoftheproblemA110fthesewereonpaperCADsystemswerenotusedinthestudgbecausenoneofthedesignersusedCADlntheirdailypractice，anditsusewouldhaveaddedanothervariabletoanalreadycomplexexperiment.Fromthemorethan40hofdatataken，15sectionswereselectedthatrepresentedtypicalconceptual，layout，detailandselectiondesignforeachsubjectThe15sectionsofprotocoldataconsistedof174rainofdataThedatawereanalyzedtoexploretheobservationsthatdrawingsareusedto：1Archivethegeometrictormofthedesign2Communicateldeasbetweendesignersandbetweendesignersandmanufacturingpersonnel3ActasananalysistoolOften，missingdimensionsandtolerancesarecalculatedonthedrawingasitlsdeveloped4Simulatethedesign5ServeasacompletenesscheckerAssketchesorotherdrawingsarebeingmade，thedetailslefttobedesignedbecomeapparenttothedesignerThis，inett)ct，helpsestablishanagendaofdesigntasksleLtoaccomplish6Actasanextensionofthedesigner’sshorttermmemoryDesignersoftenunconsciouslvmakesketchestohelpthemrememberldeasthattheymightotherwisetorgetThe1990paperrefinedandsupportedtheseobservationsAdditionalIv，althoughthesubiectsdidnotuseCADsystems，theresuhssuggestedthat：1CADsysternsnl[istallowtbrsketchinglnput2CADsysternsnlustallowforavarietyofInterfacestbrthedesignerThisdoesnotmeanmorewaystodefineacircle、butaneftorttomatchtheinterfaceandtheimageontheCADsystemtothatneededbythedesigner3CADsystemsiiltlStrecognizedomaindependentfeaturesandtreatthemasentities4CADtoolsneedtobeabletomanageconstraints(evenabstractandtkmctionalconstraints)andensuretheirsatistaction、asitisevidentthathumandesignersarecognitivelylimitedinthisabilitySincethatpaperwaswritten，CADsysternshavematuredandhaveaddressed、atleasttosomedegree、all南uroftheconclusionsiIowever，eventhemostrecentsystemsareaongwaytbomtheidealmechanicalengineeringdesignsupportsystemInthispaper，theidealsystemwillbedescribedandprogresstowardthisldealdiscussed2Amodelofdesignproblemsolvingitmaysomedaybepossibleforadesignertoputona‘‘thinkingcap”thatcantakehisorherthoughtsanddeelopahardwarereDresen【atlonResearchonunderstandingcognitiveprocesses，CAD，andrapidprototypinglscertainlymovinglnthatdirectionThisidealimpliesthatwecantbrmtflateconceptsJnourheadsthataresumcientlywelltormedtowarranthardwareItalsoassumesthatCADsystemsaresuflicientlgdevelopedtotakeourthoughtsandmanagetheevolutionofpartsandassembliesCADsystemdevelopmentwillrequireantinderstandingofthecognitiveworkingsofdesignerssothatthetransitiontbomthoughttorepresentationispossibleToexplorewhatlsknownaboutthislink、considertherelationshipbetweenthehumanproblemsoh,erandtheexternalenvironmentshowninFig1ThisfigurelsbasedonthemodeldevelopedbvNewellandSimon『20landlscalledtheinformationprocessingsystem(IPS)Thefigureisasimple‘‘map’’ofwhereinformationaboutthedesignisdevelopedandstoredThefigureshowsaninternal，humanproblemsolvingenvironment(insidethemindofthedesigner)andanexternalenvironment(outsidethemindofthedesigner)Withinthedesigner，twolocationscorrespondtothetwodifferentkindsofmemory：shorttermmemory(STM)andlongtermmemory(LTM)Externaltothedesigner，therearemany‘‘designstoragelocations”includinggraphicalrepresentationmediasuchaspiecesofpaperandCADtools，aswellasothermediasuchastextualnotes，handbooks，andcolleaguesEachlocationhascertainpropertiesthataffecthowitcanbeusedindesignDetailonthecharacLeris【icsoftheSTMandtheLTMlsbasedonNewellandSimon’smodel[20JExtensionshavebeenmadetoitforvisualimagery【1l，12，13Jandeffortshavebeenmadetocodil~~it【21itmustberealizedthatthecontentsofthemodelgivenherearenotfollyagreedtointhecognitivepsychologycommunity，butthe),arecertainlysecureenoughtoprovideabasisfordiscussingtheroleofCADinmechanicaldesign2．1Short-termmemoryShorttern：memorglsvervfastandpowerfulThecontentsoftheSTMaretheinformationweareawareof,thatis，ourconsciousmindAlldesignoperations(。g，visualperceptionanddrawingcreation)arebasedoninformationintheSTMUnfortunately，theSTMhaslimitedcapacityStudiesshowthatitislimitedtoapproximatelysevencognitiveunitsorchunksofinformationDuringdesign，thesechunksarevisualimagesofforn：s，informationaboutfonction，mentaln：odelsoffit，stepstorepresentanideainaCADsystem，orotherdiscretepiecesofinformationAlthoughlimitedincapacity，theSTMisafastprocessorwithprocessingtimesontheorderof100nls[412．2Long。termmemoryThelongtermmemory，ontheotherhand，hasessentiallyinfinitecapacity，butaccessisslowAccesstoLTMisalsonotdirectMemoriesrntlStbetriggeredbysomecueorretrievalstrategybasedonintbrmationinSTMDuringdesign，partsofthedesignarestoredinLTMThesearerelativelyeasytocuebecause，atanytime，currentlyin：portantpartsofthedesignareintheSTMandcanactaspointersfortheknowledgeintheLTM2．3ExternaIenvironmentintheexperimentsrunin1990[291，itwasclearthatmanydrawingactionswerenotusedtodocumenttheresultsofthedesignactivitybutwerepartofthedesignprocessitselgifthesubjectscouldbareperformedtheseactivitiesintheirheadstheywouldhavedonesowithoutmakingthesketches，notes，andcalculationsonpaperThus，itisconcludedthattheexternalenvironmentlsoftenusedasanextensionoftheSTMandLTMitlscriticalthatthemediausedinthisenvironmentsupportthedesigner’scognitionItemizingthematchormismatchbetweenthemediaandhumancognitionisoneoftheobjectivesofthispaperTheapproachtakeninthispaperistofirstdescribethetypesot'informationmanaged(Sect3)andthendiscusstheactivitiesperformedbytheexternalenvironmentsupportingthedesigner(Sect4)ThetypesofinformationandactivitiesaredevelopedintermsofthecapabilitiesofanidealsystemEachsubsectionbeginswithstatementsaboutwhattheidealengineeringdesignsupportsystemshoulddoSupportinginformationfollowsthesestatementsNext，thereisadescriptionofhowpaperandpencil，2DCADsystems，solidmodelingsystems，parametricsystems，andothersupporttoolsmeettheidealEachsubsectionconcludeswith0DD0r【unlLlesforlmprovement3Informationmanagedbyanidealmechanicalengineeringdesignsuppo~systemMechanicalengineersmanageabroadrangeofinformationinthissection，theXarioustypesofinformationwillbeitemized，beginningwiththemostbasicandprogressingtothemostdemanding3．1Form，fit，andfun~ionTheidealengineeringdesignsupportsystemshould：1AllowdesignerstoworkI?omdes￡redJunctiontotheothertypesojlnlornlation2Allowdesignerstoflexiblyworkonthearchitecture,shape,^f，andfunctionofpartsand(zss0川bliesThemechanicaldesigncommunityhastraditionallythoughtintermsofform，fit，andfunctionFigure2showstheinterplayamongthesebasictypesofinformationthatdescribetheproductbeingdesignedGenerally，thereasonfortheobiectbeingdesignedistofulfillsomedesiredfunctionsTheformofthepartsandassemblies，andthefitbetweenthem，dependonthedesiredfunctionoftheproductThus，theidealsystemshouldallowthedesignertoworkffonlfunotiontofornlandfitTheterm‘‘form’’actuallyimpliesboththearchitectureandtheshapeofpartsandassemblies(Fig3)Theterm‘a(chǎn)rchitecture’’hascometomeantheskeletalstructurethatmapsthefunctiontotheformArchitectureisthe‘‘stickfigure”thatcanbeeasilymanipulatedandchangedbeforetheshapeisrefinedShapeimpliesthegeometrythataddshodVanddetalttotnearcnltectureuttendeslgnersi~l-stdevelopthegeneralarchitectureoftheobjectbeingdesi~dnedthenadddetaitsaboutshapean(1fitWherewPn憎todayEngineersgener~dlyworkfromtheftnlctionofasystel~、tothearchitectureofanassembly，totheshapeofpartsiaunctionoccursprimarilyattheconnectionsorfitsbetweenthepartslnanasselnblyillotherwor(1smnctionlsdevdopetllnassemb[ieslhisbelngsaid，CADsystemshaveprimaliLysupportedtheforlnorgeometrydevetopnlentotpartsPaperandpenci[attm~seasysketchingofarchitecturewithstickfi~uresandtheirevo[utiontoconlponentsPaperandpencilatsosupports[imitedfunctionnlodelingthroughsketchinl4actionsthatshowlnotionorflowlnassemblies『9、14]Both2DCA／3systemsandpaperandpencilarefimitedtosimpleinputoflineseglnentstorepresenttheedgesofCOlnponentsSolidnaode[ingsystelnsarestiltColnponentorientedeventhoughtheysupporttherepresentationofedges，surfl~ces，andsotidsParametricsystemsgleaflylniprove(1thelllode[illl4offornlwiththeIimltedabilitytomodeInt…das…bllesFuturesystel~SneedtohelpthedesignervisualizefllnctionbeforegeometryisfullydefinedComputersystenlsareallowingbetterrepresentationoffllnction，。g，kinelnatic，dynamic，fluidflow，andvirtmdrealitysystemsWiththecontinueddevelopment0fCOlnputersupporttoolstheabilitytoworkfr0111fllnctiontoformwill…tlnl_e呲v0LveCA／3systemstodatehavebeenpartdrivenPartsaredevelopedandthenfitteclto~ethertomakeanassemblyIhecontributionsoftheIayOtltdlawinKhavenotbeenwe[1supportedParalnetricsystemshavebeguntol~OVetoanlorenaturalflow，butparametricnlode[ingrequiresthedesignertoPIanaheadoftimethegeometricconstraintrekltionshipsthatdefinethepart,MallyparametricsystellsrefertotheorderlngoftheconstraintsasthedesignintentIhismethodo[oD"，whilelnovingto~ardtheide~d，doesnotwellsupportthedesignerasthep[allllillgneededadclsburdenandtheorderin~nlaynotbeknowniniti~fllyandlnaychangeduringthedeve[oplnentFurther，“designintent”asusedillparametricsystemsistoo[imiting(seediscusslonofdeslfanIntentbelowlOpportunIExtendCADsystemsto~d[owthedesignertodevelopthearchitectureofpartsandassemb[iestomliltlneede【lmnotionfheynltlstatlowthedesignertoworkfr0111thearchitecturetotheshaDean(1fitoftheconlponentsthemselveslhiswi[1requireworkinl4wlthabstractionsofpartsan(1asselnbIiesaswe[1asbuildlngthegeometryofobjectsfromtheirarchitectureandinterfaceswithotherobjects3．2MaterialandmanufacturingTheidealengineeringdesignsupportsystemshould：3Integratetheman@zcturingandassembl),practicesand(oltlltl01,1materialusageoythecompan),oritsvendorsOneofthecornerstonesofconcurrentengineeringistheintegrationofthedevelopmentoftheproductandtheprocessesthatsupporttheproductKeyamongtheseprocessesarethoseusedtomanufacturethepartsandassemblethemTheseactivitiesalsodependontheselectionordevelopmentofthebestmaterialsfortheproductThus，asshowninFig4，thebasictbrm(architectureandshape)，fit，andfonctionneedtobetiedtomaterials，manufacturing，andassemblyWherewenretodi9,Currently、therearesystemsthataidinthedevelopmentofinjectionmoldsandsheetmetalpartsflowever，formostmanuthcturingandassemblymethods，onlytextnoteshavesupportedthisnongeometriclnformationOpportuMt),ExtendCADsystemstoprovidethedesignerwithintbrmationaboutanticipatedmaterialandmanul；acturingmethodsThisneedstobepersonalizedaseachcompanyandvendorhascertainmaterialsandmanutacturingandassemblymethodsthatarestandardandwellknownKnowledgeabouttheseshouldbeeasilyavailabletothedesignertoaidinthedevelopmentofpartsandassemblies3．3CostTheidealengineeringdesignsupportsystemshould：4Supporttheengineersosheorheisctlv(~re。lthee‰ect。feachJblturechange01,1costⅢitisgeneratedThecosttomaketheobjectbeingdesignedisnotapart0fitsdescription，yetitisamajorfactorinalldesignconsiderationsItisshowninFig5ascloselytiedtothematerialusedandthemanufacturingmethodandthroughtheseindirectbtotheftinctionandfornlOftenthereisadisconnectionduringthedesignprocessbetweendrawingwhatisbeingdesigned，butthelimitationsandtargetsonitAssuch，itiscriticalinformationAsshowninFig6，therearerequirementsonat[theothertypesofinformationpreviouslydiscussedTraditionally，engineershavedoneapoor]obatdevelopingrequirementstbrproductsWher~w。(It6"tod~9,Oneofthebestpracticescurrent[},usedtodeve[oprequirementsinindustryisqualityfunctiondep[oyment(QFD)[7，321Manycompaniesusetheresultsofthismethodtodirect[},feedrequirementstothedevelopmentofcomponentsandassemb[iesAdmittedly，manyoftherequirementsdeve[opedwiththeQFDareforfunotion；however，therearea[waysmanyconstraintsonbothfunctionandgeometrythatdrivethedevelopmentofpartsandassemb[iesTodate，thisisnotwe[1integratedwithCADsystemsStauffer【26Jshowedthatasthedesignprocessn~ovesfromconceptualthrough[ayouttodetaildesign，thesourceofconstraintsmovesfromthoseimposedfromoutsidethecontrolofthedesignertothosebasedonpreviousdesigndecisionsThisimp[iesthatnotonlyshou[drequirementslikethosedeve[opedusingQFDtypemethodsbeintegrated，butthereasoningbehindearlierdecisionsalsoneedstobesupportedThiswit[befurtherdiscussedintheseclionondesignintentfSect361OpportunityCADsystemsneedtointegraterequirementsandconstraintsintothedeve[opmentofpartsandassemblies3．5IssuesandplansTheidealengineeringdesignsupportsystemshould：6Supportthedevelopment，Jbllowing,andupdatingplans7SupportthelmtrlagemenlissuesnotphtnnedJot．Whereasat[thetypesofinformationdescribedsoihrrepresenttheartifactsbeingdesignedandtherequirementsonthem，thelot[owingtypesofinformationrepresenttheprocessthroughwhichtheartifactsaredevelopedTheimportanceoftheprocesshasbeenaconcernlnindustrysincetheearh1980sandanareaofresearchsincethemid1980sThetiebetweenproductandprocessisamaiorpartofconcurrentengineeringinthelate1990s，thisconcernbecameprominentwiththedevelopmentofinterestinintegratedproductandprocessdevelopment(IPPD)，thesuccessortoconcurrentengineeringTraditionally，theproductdesigncommunityaddressesthedesignprocesslntermsofthetaskstobecompletedindexelopinganewproductThesetasksarefocusedonspecificdesignlssuesthatcanbeplannedtbrinthedevelopmentoftheproductHowever、manyissuesariseduringthedesignofaproductthatcannotbeplannedtbrThislsespeciallytrueduringthedevelopmentofnewproductsorduringtheuseofnewtechnologiesFigure7showsthatlSStlesandplansaddressalltypesofrequiremeritsandproductinformationissuesortasksinproductdesignrequirethedesignertodevelopnewlnformation0neofthefirstexperimentsaimedatunders【andinghumanIntbrmationprocessingduringdesigntasks【27JshowedthatovertwothirdsofthestrategiesusedbythedesignengineersduringthedexelopmentofnewproductsweresearchesthroughdesignspaceSearchesimplythatthereisarangeofpotentialsohltionstoeveryissueandthatthedesignermustlookatseveraloftheseahernativesolutionstodeveloponethatlssatisfactorySearchstrategiesarewellstudiedbytheartificialintelligencecommunityThreetypesofstrategiesdefinedbycomputerscientistsandidentifiedinthecognitivestudywere‘‘generateandtest”，‘‘generateandimprove”、and‘‘meansendsanalysis”Ineachsearchtype，thedesignerdevelopsandrefinesthealternativesandcomparesthemtotherequirementsuntilson2esatisfactorychoicehasbeenmadelnthetimevailableBasedonthesefindings、inordertosupportdesigners，systemsmustnotonlytrackthecompletionofplannedwork，butmustalsosupportthedevelopmentandmanagementofmultipleahernativesforallissuesaddressedWherewenretodi9,Projectplanningandchangen2anagementhasalwaysbeenalargepartofengineeringmanagementProductdatamanagement(PDM)systemshavemadelargestridestowardintegratingtheactualdesignworkwithwhatwasplannedThesesysternsarestillmaturingOpportunityComputersupporttoolsneedtocontinuetoevoh,etoassisttheengineerindevelopingtheproductandtheprocessinanintegratedfashion3．6IntentTheidealengineeringdesignsupportsystemshouldmanageallthepreviouslydefinedtypesofinformationinadatabasepit,s：8SupportznfoH}{nlionaboutproblemsol"issllesaddressedt。g?businessisslles?planningissues?andartiJactdesign￡SSlies)9SupportlHiormationabouta1"glltllenlsjbl"01"againstalternativesf。g，qualitativediscussion，quantitativeanal),sis,rules,andstandards)based0nrequirements10SupportlnibrmationaboutthedecisionsreachedAnumberofauthorshaveexploredtheconceptofrecordinga‘‘designhistory”Nearly15yearsago，Mostowstatedthattherewasagrowingconsensusintheartificialintelligencecommunitythat，‘‘a(chǎn)nidealizeddesignhistoryisausefulabstractionofthedesignprocess”【191Inthelate1980s，thisauthorandhiscolleaguesbuiltanobjectorienteddatabasethatorganizedinformationaboutthedesignofasimplemechanicalsystem[5,6，301Thisdatabasecouldbequeriedabouttheevolutionofconstraintsandtheeft~ctofdecisionsontheartit3ctsbeingdevelopedSinceMostow，theartificialintelligencecommunityhasbeenactiveindeveloping‘‘designrationale”systemsAworkshopheldin1992【16Jdefinedthetermrationaleat‘a(chǎn)nexplanationthatanswersaquestionaboutwhyanartifactisdesignedasitis”Baxter【31，inhisthesis，refinesthedefinition：‘‘Designrationale：aninformationstructurethatjustifieshowtheimplementation(consequencesofthedesignselectionslsatisfiesitsspecification”ThisdefinilionemphasizesthestructureofthedesigninlbrmationandtrackingtherelationofdecisionsbacktothespecificationsAnothercommunity，whichisorganizedarounddevelopmentoftheSTEPIVstandard，usestheterm‘‘designintent”Theiruseofdesignintentreferstothecauseandeffectrelationshipsamongproduc【dataInanunpublisheddocument，aSTEPIVresearchersrates：“Generally，thetermintentmeansthepurposeorplanforperlbrmingactivitiesDuringproductdesign，theseactivitiestransformasetofrequirementstothefinalsDecincaflonsforproductionInabasicsense、theintentistheblueprinttbrtheevolutionoftherequirementsIntotheproductionsDeclncatlonsThisblueprintnotonlyhasintbrmationaboutthedevelopmentofthegeometry，butalsoontheevohltionoftheproductfunctionandbehavior，therationaleunderlyingdesigndecisionsandthelnfluenceofbusinessactivities’’intheCADcomnlunity、thetermIntentlsusedtodescribetheorderingofgeometricconstraintequationsinaparametricsystemThisorderingdefinesthegeometricdependencyneededbythesystemlnordertomakechangesandisnotnecessarilythecognitiveorderingthatwastollowedbythedesignerinthedevelopmentorrelinementolthepartorassemblyFinally、insomebusinessliterature、thetermcorporatememorglsusedtoemphasizethefeelingthattheinlormationmanagedisbeyondthatassociatedwiththetraditionalartit：actas1tlncludesbusinessinformationaswellintheresuhsofthefirstCERCWorkshoponEnablingTechnologies【21J，thediscussiononcorporatememorywasinterms0idesignhistoriesandrationalesSupportingfulldesignintentintormationmayevenbemorecomplexthanstoringwhathasbeengeneratedduringdesignGruber『8lclaimsthatitlsnotsufficient]us【tocapture、store、andretrievethesamelnformationlieobserves：“rationales(intentslareconstructedandlnferred廳onlstoredlnformationratherthanascornpleteanswers”inotherwords、designintentsystemsmayhavetoanswerquestionsthatreqmreinIormationdillerentthanthatcapturedThequestionsthatariseduringquerymaynotbeanswerablewithonlythelnformationoftheoriginaldesignThisimpliesthatthedatamustbestrutturedduringcaptureorstoragesothatanswerscanbedevelopedtoneededquestionsDesignintentsystemsmustrecordandmanageinlormationthatshowswhyandhowadecisionwasmadeabouteachissueaddressedAsshowninFig8，adesignintentsystemneedstosupportallthetypesofinformationpreviouslydevelopedandstorethisinformationinaneasilyindexeddatabaseWherewe~tl,etod~9,Tocapture，store，andallowqueryofthedesigninformationisachallengingresearcharea[31JToalimiteddegree，PDMsystemsarebeginningtomanagesomeoftheneededinformationttowever，thesesysternstendtobeorientedtowardlnformationthatlswellrefinedandnotevohltionaryinformationFurther，thesesystemsdonothaveaformalmechanismformanaginginformationaboutargumentationleadingtodecisionsParametricandvariationalsystemsallowfordesignreuseThus，itiseasytofindtheanswertoqueriesabouttheeffectofformchangesandsensitivitiesInthismanner，thesesystemshavecapturedsomeoftheintentbehindthelnformationmodeledOnelimitationofthesesysternsisthattheycanonlybeusedwithgeometricdecisionsanddecisionsaboutbehaviorthatcanbegeometricallymodeledAdditionally，thesesystemsdonotmodeltheactualdecisionstructureTheyonlyrecordtheorderinitiallyanticipatedtogivethesystemnecessarygeomemcteasoningIfthevalueofaparameter(i．e，thelengthofapart)isqueried，parametricsystemswillgiveinformationaboutthislength’sdependencyonotherdimensionsofthepartilowever，itdoesnotgivetherationalefortherelationsortheargumentsforthecurrentvahleAnumberofCADcompanieshavebeguntoofferdesignnotebooksthatallowthedesignertokeepnotesabouttheexoMngproductsThesenotebooksarethefirststepinsupportingneededactMtiesandinformationmanagementilowever，itisbelievedthatadditionalstructureandindexingwillbenecessarytoachieveusefuldesignrationalesupportsystemsOpportunityThereisgreatpotentialinthisareaforimprovingthedesignprocessandthereuseofinformationCADsystemshavebeguntocaptureandmanagetheneededinformation4Idealmechanicalengineeringdesignsuppo~systemactivitiesTherearesevenactivitiesthattheexternalenvironmentprovidestothedesignerregardlessoftheinformationmanagedandmediausedTheseactivitiesserveasdimensionsformeasuringtheexternalenvironment’sabilitytoaidthedesignerTheactivitydiscussionisbasedonthatpresentedinIssuesCriticaltotheDevdopmentoyDesignHistory,DesignRationaleandD~signIntentstems【31J4．1Suppo~informationdevelopmentTheidealengineeringdesignsupportsystemshouldsupportthemaniptflationofthedifl)renttypesofinformationand：11Matchthespeed可theshortterm111elliot),during10rmaliondevelopmenteffectrelationshipsamongproductdatainanunpublisheddocument、aSTEPIVresearcherstates：“Generally、thetermintentmeansthepurposeorplaniorperformingactivitiesDuringproductdesign，theseactivitiestranstormasetofrequirementstothefinalsDeclncatlonsforproductioninabasicsense、theIntentistheblueprintibrtheevolutionoftherequirementsintotheproductionsDecinca【ionsThisblueprintnotonlyhaslnformationaboutthedevelopmentofthegeometry，butalsoontheevohltionoftheproductfunotionandbehavior，therationaleunderlyingdesigndecisionsandtheinfluenceofbusinessactivities’’IntheCADcommunity、thetermIntent1susedto