SHADE:TechnologyforKnowledge-Based JamesG.McGuireDanielR.Kuokka CollaborativeEngineering kuokka@aic.lockheed.com,mcguire@aic.lockheed.com LockheedPaloAltoResearchLaboratories JayC.WeberJayM.Tenenbaum 3251HanoverStreet,O/96-20B/254F EnterpriseIntegrationTechnologies PaloAlto,Ca.94304-1191USA ThomasR.GruberGregoryR.Olsen weber@eitech.com,tenenbaum@eitech.com StanfordKnowledgeSystemsLaboratory PaloAlto,Ca.94301USA 459HamiltonAvenue gruber@sumex.stanford.edu,olsen@sunrise.stanford.edu Stanford,Ca.94305USA CAEsystemstendtolimitexibilityandprocessinnovation.TheSHADE(SHAred CAEsystemstendtoisolateinformationattoolboundaries,andtypicalintegrated productdevelopmentandintegratedmanufacturing.however,typicalspecial-purpose Eectiveinformationsharinganddecisioncoordinationarevitaltocollaborative Abstract DependencyEngineering)projectstrikesabalancebetweentheseundesirableextremes ducers. content-directedroutingandintelligentmatchingofinformationconsumersandpromationexchangeforchangenoticationandsubscription,andfacilitationservicesfor representation(languageanddomain-specicvocabulary),protocolssupportinginfor- CAEsystems.SHADE'sapproachhasthreemaincomponents:asharedknowledge bysupportingrecongurableexchangeofengineeringknowledgeamongspecial-purpose somethingisalwayschanging-perhapsadesignrequirementanunanticipatedsimulationor 1Introduction Attheheartofeectiveconcurrentengineeringiscommunication.Inproductdevelopment, testresult,theavailabilityofacomponent,oranimprovementtothemanufacturingprocess. oftheirdecisionsoneachother,andnotifytheaectedpartiesinanappropriateway. Reactingquicklytosuchchangesisessentialforqualityandproductivity,andgettingthe informationtotherightplaceisanessentialprerequisite.designersneedtoassesstheimpact 1

tofacilitateinformationsharingandcoordination.infact,currenttoolsoftenaggravate theproblembyisolatinginformationattoolboundaries,creatingislandsofautomation. Mostcomputertoolssupportspecictasksinengineering(e.g.,geometricmodeling,analysis),manufacturing(e.g.,processplanning,scheduling)orbusiness(e.g.,cashowanalysis). Whilecomputersareusedextensivelyinproductdevelopment,existingtoolsdolittle membersinotherdepartments.thoseindividualsmustthenre-entertherelevantinformationintheformatrequiredbytheirtools.duetothisineciency,designersendupmaking decisionsonthebasisofinconsistentorout-of-dateinformation. cess[16,30],wearedemonstratingaexibleinfrastructureforanticipatedknowledge-based, oftheconcurrentengineeringproblem.ratherthanattemptingtomodelthedesignpro- provideamediumthatallowsdesigners,throughtheirtools,toaccumulateandshareengi- machine-mediatedcollaborationbetweendisparateengineeringtools.oursolutionisto TheSHADEproject[10]isprimarilyconcernedwiththeinformationsharingaspect However,thetransferofrelevantinformationfromonetooltoanotherissometimesimpossible.Often,theonlyoutputofonetoolisapieceofpaperthatismailedorfaxedtoteam customizedtotheknowledge-sharingneedsofparticularprograms.thisismorefocussed, andtherebymoreexible,thanapproachesthatpursuevocabulariesthatencompassall neeringknowledgespanningthefunctionalityofindividualtools.thisinvolvesmorethan establishingbitwaysbetweenprograms;itrequiresatleastthreeadditionalfunctionallevels. exchangedescriptionsoftheirinformationneedsandcapabilitiesdynamically.thisprovides programssimultaneously(e.g.,pdes/step).second,thereisameansforprogramsto Therstlevelisaknowledgerepresentationlanguagewithavocabularythatcanbe belarge,theremustbeasetofservicesthatfacilitatethecommunication,o-loadingthe othermodel-basedapproaches[e.g.,20,28,29].shadeisdistinctfromtheseapproachesin burdenontheindividualteammembersandtools. exibilityinsysteminteractions.third,sincetheoverheadofincreasedcommunicationcan itsemphasisonadistributedapproachtoengineeringknowledgeratherthanacentralized icallycentralizedknowledge,butthemodelingvocabularyisdistributedaswell,focusing modelorknowledgebase.thatis,notonlydoesshadeavoidtherequirementofphys- SHADE'suseofknowledgerepresentationforCAEsysteminteroperationdraws>from knowledgerepresentationonspecicknowledge-sharingneeds. issues.pact[2]isalandmarkdemonstrationofboththecollaborativeresearcheortand SharingInitiative[21,22]isacommunity-wideeorttoprovideanadequaterepresentational ofagent-basedtechnology.workonfederationarchitecturesandagent-basedsoftwareengineering[7]hasservedasabasisformuchoftheresearchinthisarea.thearpaknowledge SHADEisjustoneprojectwithinalargercooperativecommunitylookingatrelated frameworkformanyprojects.theknowledgecentereddesignproject[14]isfocusingmore closelyontheproblemoftransformingexistingtoolsintoagentsthatarecapableofcommunicatingviatheshadeinfrastructure.anotherprojectatlockheed,calledcosmos[19],is focusingonprovidingsupportfornegotiationandcommitmentreasoningwithintheshade lyingtechnology.section4isdevotedtothedescriptionofseveralapplicationsofshade exchangetechnologiesinordertohelpengineersanddesignerscollaborateinmechanical domains. infrastructure.finally,theshareproject[25]islookingatawiderangeofinformation Section2givesabriefoverviewoftheSHADEapproach.Section3describestheunder- 2

technologyillustratingthematurityoftheresearch.finally,weprovideanappendixdescribingtechnologywhichisavailablefordissemination. ThreebasiccomponentsareembodiedintheSHADEapproachtoagent-basedintegration, 2Approach permitknowledge-levelexchangesofinformationaswellasmessage-levelexchanges.finally, correspondingtothethreerequirementsoutlinedabove.firstacommonvocabularymust asetofbasicfacilitationservicesisrequiredthato-loadfunctionalitysuchasnameservice, bedenedthatallowstoolstoexchangedesigninformationandexpressshareddependencies overthatinformation.second,asetofcommunicationprotocolsmustbeestablishedthat TherstcomponentofSHADEisasharedontology:aformalspecicationofashared 2.1SharedRepresentationtoBridgeToolPerspectives conceptualizationthatprovidestherepresentationalvocabularywithwhichagentscancommunicate[12].theneedforasharedontologyisadirectresultofthemulti-disciplinary manufacturing),eachwithalargelydierentlanguage.however,thevariousperspectives natureofengineering.therearemanydierentviewsofadesign(function,performance, resentationandvocabulary. tionshipsamongparticipatingagentsusedinmulti-disciplinarydesignactivities,thisdoes notimplythatitmustbecapableofexpressingtheunionofalldistinctionsmadebyparticipatingagents.manyportionsofadesignspaceareofinterestonlytooneagent,whileother portionsmustbecommontomanyagents.thechallengeistosupportdierentdegreesof Whereasthelanguagemustbedemonstratedasbeingexpressiveenoughtobridgerela- buering,routingofmessages,andmatchingproducersandconsumersofinformation. typicallyoverlap,necessitatingthesharingofinformationifdesignistoproceedconcurrently andcooperatively.forinformationtobeshared,theremustbeacommonlyunderstoodrep- amongopaqueelements(\objectxisinsomewaydependentonobjecty")tothegradual knowledgesharing,>fromarms-lengthknowledgeexchangestostrongcommonmodels. introductionofcommonmodels(\y:b=2x:a+3")toexplanationsofcausality(\x tools.thelanguageevolutionwouldproceedfromanencodingofsimpledependencies evolutionoflanguagethatallowstheencodingofprogressivelyricherdependenciesacross SHADEacknowledgesthisrangeofknowledgesharingbypresupposinganincremental noticationandinteractionamongdesigners.ofcourse,italsoimposesgreaterdemands causedytofail").thisevolutionwouldenableincreasinglysophisticatedtypesofchange uponthesupportingcommunicationsinfrastructure. andtherelatedvocabularyismodularizedintohierarchicaltheories.therepresentation, extensibility,ontologiesaredenedwithinawidelyaccepted,formallydenedrepresentation, forengineering.toestablishconventions,promoterigor,andfacilitateenhancementand andtechniquesforbuildingontologies,andapplyingthemtoconstructspecicvocabularies Tobettersupportthedevelopmentofsharedontologies,SHADEisworkingonsystems tools,techniques,andtheoriesarediscussedbelow. 3

ofstandardslikesql.withoutaneorttounderstandandstandardizeagentcommunication,therewouldbeaproliferationofincompatible,adhocagentcommunicationlanguages. 2.2ProtocolsforCoordinationAmongTools Knowledge-basedagentsinteractinmanywaysbeyondthesimplequery-responseparadigm SHADEisworkingondeningacommonagentcommunicationlanguage(asetofmessage withcommunity-widestandardseortstoensurebroadacceptance. schemata)thatpermitthesharingandexchangeofknowledgeencodedintheontologies outlinedabove.sincethesemessagesmustbecommontoallagents,shadeisworking infrastructure.theelementsoftheshareddesignmodelareactuallydistributedamongthe wrapper'sknowledgebase).toberecognizedasaninformationservicecontributingpartof (eitherembeddedwithintool-specicdatastructuresorcontainedwithintheencapsulating individualagents.eachindividualagentmaintainsaportionofthesharedsetofbeliefs Bywayofexample,consideradesigntoolinteractingwithothertoolswithintheSHADE thevirtualknowledgebase,anagentsendsamessagetoadvertiseitsinformationproducing potential,orcapabilities.conversely,anagentsendsamessagetodeclareitsinterestsin making.advertisementsandinterestscreateavirtualsharedknowledge-basedeventhough relevantportionsofthesharedmodel,therebyenablingnoticationandinformationmatch- theactualinformationisdistributed. 2.3FacilitationAgentstoEasetheCommunicationBurden ThethirdmajorcomponentofSHADEisan(extensible)suiteofcoreframeworkservicesto individualagents.theseservicesareimplementedbyspecialfacilitationagentsconnected facilitatecommunicationandcoordinationamongagents,therebyreducingtheburdenon totheinfrastructuremuchlikeapplicationagents. informationamongparticipatingtoolsbasedonprevioussubscriptions.thisallowsanagent Asnetworksofagentsgetlarger,thisbecomesanecessityasopposedtoaconvenience. tosendamessagewithouthavingtodetermineexactlywhichotheragentsareinterested. Arepresentativefacilitationserviceiscontent-basedrouting:theintelligentroutingof thattheyderive(thatistranslatableintothesharedrepresentation).thismakesitfeasible foralogicallycentralizedfacilitatortocheckallnewinformationagainstinterestcriteria androuteinformationappropriately.theawinthisschemeisthatanagentcanproduce manytypesofinformationand(assumingapayforaservicescheme)probablywillnot Forcontent-basedroutingtowork,however,agentsmustposteverypieceofinformation infrastructuretolocateserviceproviders.suchafacilitationagentiscalledamatchmaker, postinformationunlesssomeonehasexplicitlyrequestedit.whatisneededisafacilitation andisdiscussedinmoredetailbelow. isposted.thiswouldeasetheburdenonindividualagentssincetheycouldrelyonthe servicethatlocatesinformationproducerscapableoffulllingoutstandinginterestsand managessubscriptionstotheseinformationproducingservicessothatneededinformation 4

tionshavebeendevelopedsofar.thissectionoutlinesthemajorresultstodate. TheaboveelementsofSHADEhavebeenunderactiveinvestigation.Severalspecicsolu- 3SHADETechnologyElements 3.1RepresentationofSharedDesignKnowledge relationshipsinanagentarereectedintherepresentationalvocabulary,anontologycan andtherelationshipsthatholdamongthem[5].aconceptualizationisanabstract,simplied viewoftheworldthatwewishtorepresentforsomepurpose.sincethesetofobjectsand Anontologyisanexplicitspecicationofaconceptualization.Aconceptualizationisdened begivenasasetofdenitionsforthissharedvocabulary. bytheobjects,concepts,andotherentitiesthatarepresumedtoexistinsomeareaofinterest Initiative.KIFisamachine-readableversionofrstorderpredicatecalculus,withextensions implementation-andagent-independentformat.theformatusedinshadeiscalledkif toenhanceexpressiveness.kifisthecontentlanguagefortheshadeframework.thekif (KnowledgeInterchangeFormat)[8],whichisaproductoftheARPAKnowledgeSharing Thecommonontology,andthesentencesusingthatontology,mustberepresentableina specicationdenesthesyntaxandsemantics;theontologiesdenetheproblem-specic vocabulary;agentsexchangesentencesinkifusingthesharedvocabulary. maintainportableontologiesbyprovidingtranslationmechanismsintoandoutofashared representation.consequently,shadeisusingtheontolingua[9]systemtodevelopand maintainitsontologies.ontolinguaprovidesalayerontopofkifforwritingdenitionsand translatingthemintoimplementedrepresentationsystems.ontolinguacantranslateclass, Sinceindividualengineeringtoolshavespecializedinternalformats,thereisaneedto specializesintranslatingtoobject-centeredrepresentations,suchasthoseusedinframe systemsandobjectorienteddatadescriptionlanguages. relation,function,andobjectdenitionsintoseveralknowledgerepresentationsystems.it developers.thepdes/stepstandardsprovideacapabilitytospecifymachine-readable dataispartiallydescribedintextdocuments,butmuchisunderstoodonlybyapplication canbeexchangedbetweenapplicationprograms.ingeneral,thesemanticsoftheshared changestandards.dataexchangestandardsprovideaneutralformatthroughwhichdata Thedevelopmentofontologiesismotivatedbythesameneedsaddressedbydataex- allowsonetodescribeobjectclasseswithattributesandinheritance,whichoerslimited denitionsofshareddata.theexpresslanguageusedtostatepdes/stepstandards formalsemanticsforthedata(i.e.,fordatabaseoperations).usingproceduralconstraints, commitmentstoconceptualizationsoftheworldinthecontextofwhichthisdataisinterpreted.anontologygivesalogicaltheoryaboutthesharedworld,whichincludesthe ontologiesaremoreexpressiveandlesscoupledtoimplementations.conversely,dataex- Whiledataexchangestandardsstatecommitmentstocommondata,ontologiesspecify onecanputadditionalsemanticrestrictionsonthedata. vocabularyforstatingfactsaboutthatworld.sincetheyaredescribedbyrst-orderlogic, changeagreementsprovideameanstorepresentaparticularsetoffactsworthexchanging. theapplicationdeveloperswhoagreeonarestrictedsetofdatatoexchange.wecanuse Eventhoughlessexpressive,dataexchangestandardstendtoprovidemoreguidanceto 5

translationtechnology,suchasontolingua,toimplementthemappingbetweenlogicalspecicationsinontologiesanddatadescriptionsinexchangestandards.thisallowsustotakmechanicalsystems.inthatdomain,wehavedevelopedontologiesthatcapturecommon ontheexchangeofknowledgeamongagentsinacollaborativedesignteamforelectro- tospecifyconceptualcommitmentsinadeclarative,application-independentform. advantageofexistingapplicationsupportfordatadescriptionswhileretainingtheexibility conceptualizationsamongvariousdomainspecialties,suchascontrols,dynamics,kinematics, andsolidmodeling.westartwiththebasiclanguageofengineeringanalysis,mathematical EventhoughSHADEisapplicabletoanyengineeringdomain,wehavefocusedmainly expressions.forexample,acontrolsengineerandadynamicistcollaboratingonasatellite designmayneedtoexchangeequationsofmotion.becauseoftheubiquityofmathematical expressionsintheexchangesofknowledgebetweenengineers,wechosetoconstructasetof engineeringmathematicsontologiestoprovideabasefromwhichtobuildadditionaltheories. themodelerandleaveimplicitmanyofthedetailsrequiredtounderstandtheequations.for othertechnicalliterature,thesenotationsfailtocapturemuchofthemeaningintendedby example,inanexpressionlike\x+kx=f(t)",itisn'tclearfrominspectionwhichsymbols arevariablesorconstants;whetherthenumbersarerealsorvectors;whetherthemodeled Whilethereexistconsistentnotationsformathematicalexpressionsintextbooksand quantitiesarestaticvalues,functionsoftime,orfunctionsoftimeandspace.distinctions equation.furthermore,thequantitiesdenotedbyvariablesarenotjustnumbers;theyare oftenphysicalquantitiessuchaslengthandacceleration.humanengineersofteninterpret thevaluesofvariablesrepresentingphysicalquantitiesbyinferringdimensionandunitsof betweenasymbolsuchasx(i.e.,apositionvariable)andthequantityitdenotes(i.e., adisplacement>fromsomereferenceposition)arenotrepresentedinthesyntaxofthe measurefromcontext. andrelationsamongthem.theoriesofunitsanddimensionsallowautomatedconversion deneclassesofquantities,algebraicoperatorsdenedfortheseclasses,andotherfunctions fordescribingphysicalquantities,makingexplicittherelationshipsbetweenmagnitudesof variousorders(reals,vectors,tensors),unitsofmeasure,andphysicaldimensions.they TheSHADEprojecthasproducedafamilyoftheoriesthatdenethebasicvocabulary amongunits.theoperatorsformalgebraiclanguagessuitableforwritingconstraintequations.metalinguistictheoriessupporttherepresentationofknowledgeabouttheformoriesindicatesthatthelowertheoryreliesontermsdenedwithintheuppertheory. theory-inclusionhierarchyoftheengineeringmathematicsontologies.alinkbetweentheo- canexchangefactsandmodelsaboutdevices.thefollowingexamplesaresentencesabout theshaftofamotor: (physical-dimensionlength) (unit-of-measureinch) TheengineeringmathematicsontologiesprovidevocabularywithwhichSHADEagents constraints(e.g.,closed-formequations,conditionalconstraints,etc).figure1showsthe (=(q.magnitude(diametershaft-a)feet)0.3) (=(q.dimensioninch)length) (=(diametershaft-a)(*3.6inch)) (quantity(diametershaft-a)) 6

aunitofmeasure,whosedimensionislength(i.e.,itisameasureoflength).thediameter ofshaft-aisaquantityequalto3.6inches;byimplication,itsdimensionislength.thelast Thesesentencescanbeparaphrasedasfollows.Lengthisaphysicaldimension.Inchis Figure1:InclusiongraphforEngineeringMathOntologies sentencesaysthatthediameteroftheshaft,expressedinfeet,is0.3. ofontologiesandontoolstoassistthisprocess.ourcurrentfocusisontheutilizationof ontologies.wearepreparingasuiteofagentsandadditionalontologiestobeusedinafollowonexperimenttothepactexperiments.throughthisexperiment,wewillexploremany practicalissuesintheuseofontologiessuchastheroleofontologiesinagentimplementation Theontologyconstructioneorthascenteredonthepracticalitiesofcreatingacoreset completeaxiomatizationsofthesubject;theycaptureseveralimportantdistinctionsthat tothefollowingsubjects:congurationdesign,dynamics,springdesign,vibration,and solidmodeling.noneofthesetheoriesareareintendedtobecompleteorevennearly otherexperimentsweareconstructingseveraladditionaltheoriesincludingtheoriesrelated andappropriatelevelsofcommitmentforspecicusesofontologies.tosupportthisand SHADEisworkingtowardthedenitionofacommonagentcommunicationlanguageto 3.2ProtocolsofInteraction supportthetransferofknowledge-levelinformation.foranystandardtobesuccessful, allowunambiguousexchangesofknowledgebetweenagentswithdierentperspectives. bytheexternalinterfacesworkinggroupofthearpaknowledgesharinginitiative. contributiontotheknowledgequeryandmanipulationlanguage(kqml)[4]beingdened itmustbewidelyaccepted.therefore,amajorpartoftheshadeeortisanongoing currentengineering(ce).ourconcernswerethreefold:tosupportdiversequeryparadigms; SHADE'scontributiontotheKQMLeortwasmotivatedbyourexperimentsincon- 7

capabilitiesandbrokeringdirectivestolocateserviceproviders. toprovideexibilityinthebundlingoftransmittedinformation;andtoprovidedirectives thatsupportacommunityofengineeringservicesbyallowingdynamicspecicationofagent existingknowninformationdoesnotsupportnotication,sincetheinterestisassumedto notiedofthechange,sotheymayassessimpact.noticationcanbetriggeredbydetection ofchangetoinformationofinterest.thetraditionalqueryorientedapproachforrequesting withintheconceptofceisthetenetthataectedpartiesofrecentdesignchangeswillbe Asimplequery-responseparadigm(i.e.,SQL)isinadequatetosupportCE.Embodied expireaftertheanswerisreturned.whatisneededisadirectivewhosesemanticsconveya persistentinterestinmonitoringclassesofinformation. bilityonthepackagingoftransmittedknowledgeinresponsetoarequest.sometoolsinour ongoingceexperimentsarebestsuitedtohandlestreamsofasynchronouslytransmitted information(i.e.,oneansweratatime).othertoolsexpectentiresetsofanswersbundledtogether.finally,sometoolsonlyhandleincrementalupdateswhicharesynchronously AnotherconsiderationintheelaborationoftheKQMLspecicationistoprovideexi- transmittedinresponsetoarequest(i.e.,arequesttocreateaninformationgeneratorand thensynchronouslyrequesteachanswerinturn). containsubexpressionsinso-called\contentlanguages".thuskqmliscomplementaryto workonrepresentationlanguagesfordomaincontent,includingpdes,kif,andobject- OrientedLanguages. KQMLisindierenttotheformatoftheinformationitself:KQMLexpressionsoften directiveandtheembeddedcontent.theseattributesincludewhothemessageis:from, whoitis:to,whatisthe:languageoftheembedded:content,what:ontologydenesthe vocabularyusedwithinthe:content,andwhattagto:reply-with.considerthekqml subscriptionbelow,expressedinthepreviouslydescribedengineeringmathontology,to AKQMLmessageisannotatedbyreservedparameterstodescribeattributesofthe monitoranychangestoashaft'sdiameter: Asubscriptionisarequesttomonitorchangeswithinthesetofinformationdenedbythe contentdescription.theembeddedcontentdescribesthethemagnitudeofsomeshaft's (monitor:fromconsumer:toproducer:reply-withupdate-111 diameter.the:reply-withparameterdictatesthevalueforthe:in-reply-toparametercontainedwithinareplymessage. evenifanappropriaterecipientexists.forwardingandbroadcastingallowthesendingagent touseintermediariestofacilitatetransport.brokeringallowstheagenttobeunconcerned casting,andbrokeringmessages.thatis,anagentneednotsendeverymessagedirectlyto thenaldestination.oftenanagentdoesnotknowexactlywhoshouldprocessamessage,or KQMLisalsoanenablerofinformation-owarchitectures,throughforwarding,broad- :content(=(q.magnitude(diametershaft-a)inches)?x)) :ontologystandard-units-and-dimensions:languagekif implementationviafacilitationagentswillbediscussedinthenextsection. withexactlywhocanprocessthemessage.thebrokerfacilitationagentisresponsiblefor againstkqmladvertisementsofcapabilities.examplesofthesekqmldirectivesandtheir ndinganappropriaterecipientfortherequest.brokeringagentsmatchkqmlrequests 8

nicationsupporttoagents.oneoftherstnecessaryservicesthathasbeenidentiedis 3.3FacilitationServices TheSHADEinfrastructureisdesignedtoincludefacilitationagentsthatprovidecommu- Figure2:Inter-AgentCommunicationviaContent-DirectedRouting thesimplestcase,asubscriptionlookslikeasyntacticpatternthatmustbeuniedagainst themessage.moregenerally,itlookslikeanarbitrarilycomplexrst-orderlogiccondition this,agentsmustbeabletoexpresstheirinterestsintermsofageneralsubscription.in interestsassertedbyotheragentsratherthanawired-inprearrangedaddress.toachieve content-basedrouting,wheremessagessentbyanagentareroutedautomaticallybasedon agentandforwaredontotherequestingagentasthoughtolddirectlybythepublisher. Figure2showsthisoperationinprocessasaseriesofmessagesovertime. Whenrelevantinformationispublishedbysomeotheragent,itispickedupbytherouting toinformationbyposingapersistentquerywithinthevocabularyofthecommonontology. thatmustbeevaluatedforsatisabilitywithrespecttoanontology.anagentsubscribes relyoncontext-specicinformationtoevaluatethenoticationcriteria.ifthemessageand thesupportingontologycontainallinformationneededtoevaluatetheinterest,asinfigure2,thentheschemeworksne.if,however,thecontent-basedrouterneedstoremember Oneissueincontent-basedroutingistheextenttowhichthecontent-basedroutermust context-specicinformation(i.e.,thevaluesofportsovertimeinsomesimulation),thenthe approachmaybecomeinfeasibleduetospaceandeciencyconcerns.withinourcurrentimplementation,informationalupdatesareexaminedbytherouterforrelevancetootheragents \tell"infigure2),andinformationalupdateswhicharealsorequeststorememberthe messagewithintherecipient'sknowledgebase(e.g.\insert").theroutingagentmakes butarenotincorporatedindiscriminatelyintotheroutingagent'slocalmodel.kqmlprovidesdirectivestodiscriminatebetweeninformationalupdateswhichcanbeforgotten(e.g. 9

providedtoitviathe\insert"directive. theassumptionthatanycontext-specicinformationwhichitneedstorememberhasbeen Theawinthecontent-basedroutingapproachistheassumptionthatagentsvolunteer Figure3:Requesthandlingandservicelocationviamatchmaking whoareunawareofeachotherneedsandabilities.asthecommunityofservicesgrows,this enablesdesignactivitytobereconguredtoincorporatenewlyavailablefunctionality.for ofmatchmaking.amatchmakerestablishesconnectionsbetweenproducersandconsumers growsandnancialissuesareconsidered.toovercomethisproblem,wedevelopedthenotion allinformation-anassumptionthatcannotbesupportedasthenetworkofavailableservices thispurpose,kqmlprovidesthe\advertise"directivetoallowdescriptionofthekqml messageswhichanagentiscapableofsupporting. developmentoftractablealgorithmsthatinfermatchesoninterests.still,itisdesirableto oncapabilities,prudencedictatesthatthespecicationbesomewhatgeneraltoallowforthe allpossibleinterestrequests).evenifitwerepossibletopreciselycharacterizeallconditions query)thanitistopreciselycharacterizeanagent'scapabilities(whichneedstoaccountfor Inourexperience,itiseasiertospecifyaninterest(whichlookslikeaknowledgebase avoidover-generality,sobettermatchmakingcanbeperformed.withinanadvertisement, providedthequantitymeasuresthedimensionlength,intoacompatibleunitofmeasure(e.g conditionscanbeimposedupontheelementswithinarequestthroughuseofthe:contentconstraintparameter. inches,feet)forlength.agenta2\advertises"inkqmlthisabilitytoevaluatequantity descriptions.itusesthe:contentparametertodescribeanoverlygeneralabilitytoevaluate ConsiderthefollowingscenarioinFigure3whichreliesonthepreviouslydescribed engineeringmathontologies.agenta2isanagentcapableoftranslatinganyquantity, anyquantity'smagnitude.anyrequestwhichsyntacticallyunieswiththeadvertisement's 10

inch.aftertheunication,the:content-constraintrestrictionwithina2'sadvertisementis checkedtoseeifthedimensionof(diametershaft-a)isindeedlengthandthatthedimension unicationcauses?quantitytobeboundto(diametershaft-a)and?unittobeboundto innermost:contentisatentativematch.agenta1thenmakesan\evaluate"request.the ofinchislength.sincethiscanbeprovedwithrespecttothementioned:ontology,the :contentofagenta1's\evaluate"requestunieswithagenta2'scapability:content.this matchmakerforwardsagenta1'srequesttoagenta2. someengineeringdesignscenarios,suchasdistributedsimulationsovertheinternet. sinksndeachotherduringapreprocessingphase,theycancommunicatedirectlywitheach messagetracbottlenecksthroughacentralizedfacilitator.sinceinformationsourcesand otherthereafter.aprecompilationofmessagetracdataowisextremelyimportantin Thematchmakingservicealsoallowsformoreecientcommunicationbyalleviating 4Applications 4.1PACT SHADE'sinitialapplicationfocuswasonPACT(PaloAltoCollaborativeTestbed),aset sectiondescribesthemajorapplicationssupported. Todriveourresearch,SHADEisfocusingonspecicdesigndomainsandscenarios.This ofexperimentsinexercisingknowledgesharingtechniquesamongexistingconcurrentengineeringtools[2].thechallengeinpactwastotakefourexistingsystems,eachalready groundtheexperiments,designscenariosthatwouldbethwartedbytoolisolationwere aspecializedframework,andtointegratethemviaaexible,higher-levelframework.to collaboratingonscenariosofdesign,fabrication,andredesignofaplanarroboticmanipulator.eachteamwassupportedbyitsowncomputationalenvironmentlinkedviathepacingteams(lockheed,stanford,enterpriseintegrationtechnologies,andhewlett-packard) proposed. framework[7,24]overtheinternet.eachteammodeledadierentaspectofthemanipulatorfromadierentengineeringdiscipline:controllersoftware(nvisage[26]),rigidbody distributedsimulationexercisingeachaspectsupportedbythefourtools,andnallydesign modelexchangebetweenthecontrolsagentanddynamicsagent,ne-grainedcooperative dynamics(nextcut[1]),circuitry(designworld[6]),andsensorsandpowersystemmodeling(dme[13]).severalcollaborativedesigntaskswereperformedincludingdynamics Theexperimentsinvolvedfourgeographicallyandorganizationallydistributedengineer- explicitontologywasencodedinkifreectingtheoineagreements.agentsusedkqml exchangesnecessarytoenablethedesignscenarios.asaresultoftheseinteractions,an modicationssuggestedbythesimulation. toexpressbeliefanddisbeliefinknowledgecontent,andtofulllotheragentsinformationinterests.however,theexperimentwasnotacompletedemonstrationoftheshade approach.thepactarchitecturedidnotprovideadvancedfacilitationservices,suchas toadvertisetheirinformation-producingcapabilities,todescribetheirinformationinterests, Thedevelopersofthevarioustoolsidentiedtheformandsemanticsoftheinformation 11

wrapper,makingwrapperdevelopmentonerous. matchmakingorsophisticatedroutingofinformationbasedoncontent.insteadallsuchfacilitationsophisticationresideddirectlywithineachindividualdesignagent'sencapsulating basedonthemid-deckactivecontrolsexperiment(mace),aresearchprototypeintended tobeowninsideofthespaceshuttlemid-decktostudytheuseofactivebodymembers PACT,theSHADEprojectisdevelopingamorein-depth,ongoingscenario.Thescenariois AsamorecompletedemonstrationofSHADE,intendedtoeshoutissuesnotcoveredin 4.2MACE onvibrationcontrolinsatellites. Thescenarioisbuiltaroundtheinteractionofseveralengineeringagents: RigidBodyDynamicsAnalysis(basedonageneralmathagentutilizing GeometricLayout(basedonSDRC'sI-DEAS) Mathematica) ManufacturabilityAnalyst(basedonBerkeley/CMU'sMACHINIST) ControlsDevelopment(ISI'sMatrix-X/SystemBuild) StructuralDynamicsAnalysis(I-DEAS) content-basedroutingofmessages,andnegotiationsupportbasedonagentsfromthecosmos servicesandbuering,gatewayservicesforcommunicationbetweenlocalagentnetworks, project[19]. Thescenarioissupportedbyseveralfacilitationagentsthatperformfunctionslike:name VenderDatabase(UniversityofUtah'sPARTNET) ontologyarepropagatedtothoseagentsthatpreviouslyexpressedinterest.forexample, supportedbythesatellitesuperstructure.thechangestospecicsharedelementsofthe sincethisaectsthevibrationalmodes.thenewmodesare,inturn,propagatedtothe thestructuraldynamicsagentwillhaveexpressedaninterestinthemasstobesupported, Inthescenario,aseriesofexchangesisprecipitatedbyachangetothepayloadbeing controlsagentforincorporationintoanewcontrollaw.eveninthissimplescenario,thereis quiescence. 4.3VT SHADEtechnologyforspecicationofformalontologiesofcommonconceptualizationshas signicantadditionalcommunicationbetweenagentsbeforetheresultsofthechangereach Theexperimenthasfocusedontwoproblems:asimpleoce-assignmenttask;andelevator phus/vt[15].sisyphusisthenameofanongoingexperimentinwhichparticipants>from alsobeenappliedinanexperimentbytheknowledgeacquisitioncommunitycalledsisy- design,acongurationproblemwithmanyparametersandconstraints.theelevatordomain iswellunderstood,andhasbeenthesubjectofresearchsuchasvt[17],anexpertsystem severalresearchgroupsarebuildingknowledgesystemarchitecturesandknowledgeacquisitiontoolsforspecicproblemsinordertocomparetheirmethods,architectures,andresults. forelevatordesign,andthesaltsystemforknowledgeacquisition[18].thetaskand 12

domainhavealsobeenanalyzedandathoroughenglish-languagedescriptionhasbeenpublished[27].forthepurposesofthesisyphus/vtexperiment,thedomainiscomplexand largeenoughtoprecludesimplisticapproaches(brute-forcesearchorsimpleoptimization techniques). abletoacceptinputsandprovideoutputsusingtheformalvocabularyandtheoryofthe andtheelevatordesigndomain.theontologiesserveasaformalproblemspecicationfor theexperiment,withparticipantsbuildingagentsthatcommittotheontologies(i.e.,are munity,developedasetofformalontologiesthatdescribethecongurationdesignproblem TheSHADEteam,incollaborationwithcolleaguesfromtheknowledgeacquisitioncom- 4.4SimulationBasedDesignforSubmarines additionalrequirementsofrepresentingstructureanddesignconstraintsdeclaratively. SHADEprojectfortheexchangeofbehaviormodelsanddata.Thedesigntaskaddsthe ontology).thevtontologiesbuildupontheengineeringmathontologiesproducedbythe stratemajorimprovementsinthedesignprocessforsubmarinesandsurfaceships.thiswill SimulationBasedDesign(SBD)[3]isanARPA-sponsoredinitiativetodevelopanddemon- resultindramaticchangesinthehandlingofinformationandtheprocessofdesign.an theoperationalpersonnelthatwilltestthenewdesigninavirtualworld.theteamof inthedesignofashiporshipsystemwillbelinkedtoandabletoreceivefeedbackfrom CADdesignrepresentation.UsingtheSimulation-BasedDesignsystem,everyoneinvolved nodeslinkedtogetheronanetworkusingaconceptuallysharedproductdatabaseand3d SBDarchitectureforasubmarinedesignisexpectedtoinvolvefrom50to100computer theintegrationservicessubtaskofthesbdsystem.shadetechnologybeingleveragedby thelockheedteamfortheinitialprototypesystemincludes:thecontent-basedrouterand toestablishabaselinearchitecture.theshadeapproachisservingastheblueprintfor thematchmakingservice. Lockheed,NewportNewsShipbuilding,andSAICiscurrentlyperformingafeasibilitystudy 5Conclusion TheSHADEprojectiscreatingtechnologiestopromoteinformationsharingamongdesign toolswithinmulti-disciplinarydesignenvironments.ourstrategyistoprovideaknowledgebasedmediumbywhichdesigners,throughtheirtools,shareengineeringknowledge.there capabilities.finally,thesharedenvironmentwillbepopulatedwithfacilitationservicesto willmakeuseofknowledgetransportprotocolstocoordinatetheirinformationneedsand municateinacommonontologyrealizedinadeclarativerepresentation.second,agents easetheburdenofinter-agentcommunication.becausethesharedknowledgeisexpressed arethreekeyideascentraltotheshadevision.first,individualdesigntoolswillcom- inaformal,declarativelanguage,thesharedenvironmentcanusedeductivemechanismsto sharingandsoftwareinteroperation. wehavestartedworkonontologiesandfacilitatorsaimedatdesignrationaleanddecision- answerqueries,routeinformation,performtranslations,andotherwisefacilitateknowledge SHADEcontinuestoworkonfundamentalontologiesandsupporttools.Inaddition, 13

KQMLspecicationeort,andprototypecontent-basedroutingandmatchmakingagents maintenance[11,23].shadealsocontinuestobeoneofthedrivingforcesbehindthe havebeenimplemented.shadetechnologyhasreachedthepointwhereitisavailablefor settingssuchaspact.thisinter-projectapproachwillcontinue.theshadegroupis interactingwithlockheed'sspacesystemsdivisiontoexploreapplicationofshadetechnologytosupportcollaborativespacecraftdesignactivitiesinvolvingdynamicsanalysisand controlsdesign.theseactivitiesarereal-worldexamplesofthedesignscenariosexploredin Workuptothispointhasbeenmotivatedbyexperimentsinmulti-disciplinarydesign dissemination. thepactexperiments.shadeisalsobeingappliedtothevtdomain.finally,thecommunityofshadeusersisgrowing(e.g.,kcd,cosmos,simulationbaseddesign),but thegeneralityofourapproach.thesuccessofshadedependslargelyonthedegreeto whichwecansupportcoordinationamongnumerous,heterogeneousagents. 6Acknowledgements weareactivelypursuingtieswithothereortsintheresearchcommunitytofurthervalidate U.S.ArmyResearchLaboratory.WegratefullyacknowledgethecontributionsofourcolleaguesinPACT,KCD,andtheARPAKnowledgeSharingInitiative,particularly,Rich MarkCutkosky,andRichardFikesatStanford.WewouldalsoliketoacknowledgeMorton ThisworkwassupportedbyARPAprimecontractDAAA15-91-C0104,monitoredbythe Hirschbergforvaluabletechnicaleditingfeedback. Pelavin,BillMarkandBrianLivezeyatLockheed,andMikeGenesereth,GioWiederhold, 7References [1]M.CutkoskyandJ.Tenenbaum,\TowardaFrameworkforConcurrentDesign",InternationalJournalofSystemsAutomation:ResearchandApplications,Vol.1,No. 3,1992. \PACT:Anexperimentinintegratingconcurrentengineeringsystems",InIEEECom- [2]Cutkosky,Engelmore,Fikes,Gruber,Genesereth,Mark,Tenenbaum,andWeber, [4]Finin,Weber,Wiederhold,Genesereth,Fritzson,McGuire,McKay,Shapiro,Pelavin, [3]M.Davis,R.Evans,G.Davis,andG.Jones,\SimulationBasedDesignforSubmarines",ProceedingsoftheSubmarineTechnologySymposium,May11-131993. andbeck,\specicationofthekqmlagentcommunicationlanguage.ocial DocumentoftheDARPAKnowledgeSharingInitiative'sExternalInterfacesWorkingGroup",EnterpriseIntegrationTechnologies,Inc.TechReport92-04.1992. JHU/APL,Columbia,Md. puter,vol.26,no.1,january1993. [5]M.GeneserethandN.Nilsson,LogicalFoundationsofArticialIntelligence.Morgan KaufmannPublishers.1987. 14

[6]M.Genesereth,\Designworld",ProceedingsoftheIEEEConferenceonRoboticsand [7]M.Genesereth,\AnAgent-BasedFrameworkforSoftwareInteroperability",Proceed- Automation.1991. ingsofthedarpasoftwaretechnologyconference,meridiancorporation,arling- ton,va.1992.alsocomputersciencedepartment,stanforduniversitytechreport Logic-92-2. [9]T.Gruber,\ATranslationApproachtoPortableOntologySpecications",InR. [8]M.GeneserethandR.Fikes,\KnowledgeInterchangeFormat,Version3.0Reference ofknowledgeacquisition. Mizoguchi(editor),ProceedingsoftheSecondJapaneseKnowledgeAcquisitionfor Knowledge-BasedSystemsWorkshop,Kobe,Japan.1992.ToappearintheJournal Manual",ComputerScienceDepartment,StanfordUniversity,TechReportLogic-92-1. [11]T.GruberandD.Russell,\Generativedesignrationale:Beyondtherecordandreplay [10]T.Gruber,J.Tenenbaum,andJ.Weber,\Towardsaknowledgemediumforcollabo- 1992.KluwerAcademicPublishers. paradigm",technicalreportksl92-59,knowledgesystemslaboratory,stanford tionalconferenceonarticialintelligenceindesign,pittsburgh,pa,pages413-432, rativeproductdevelopment",inj.s.gero,editor,proceedingsofthesecondinterna- [12]T.Gruber,\TowardPrinciplesfortheDesignofOntologiesUsedforKnowledgeSharnale,LawrenceErlbauming,InternationalWorkshoponFormalOntologyinConceptualAnalysisandKnowledgeRepresentation,Padova,Italy.1993. University.ToappearinThomasMoranandJohnH.Carroll(editors),DesignRatio- [14]Kuokka,Livezey,Simoudis,andHood,\Knowledge-CenteredDesign",LockheedArti- [13]Y.IwasakiandC.Low,\ModelGenerationandSimulationofDeviceBehaviorwith ContinuousandDiscreteChanges",IntelligentSystemsEngineering,Vol.1No.2, [16]D.Mostow,\TowardBetterModelsoftheDesignProcess",AIMagazine,Vol.6,No. [15]M.Linster,\Sisyphus'92:ModelsofProblemSolving",GMD-Arbeitspapiere630. 0508. GMD,SchloBBirlinghoven,Postfach1316,W-5205,SanktAugustin1.ISSN0723- cialintelligencecentertechnicalreport,1993. [18]S.MarcusandJ.McDermott,\SALT:AKnowledgeAcquisitionLanguageforProposeand-ReviseSystems",ArticialIntelligence,Vol.39,No.1,pp.1-38,1989. Knowledge-BasedBacktracking",AIMagazine,pp.95-111.1988. 1,1988. [17]S.Marcus,J.Stout,andJ.McDermott,\VT:AnExpertElevatorDesignerthatUses [19]Mark,Schlossberg,Ogata,MacGregor,Kuokka,Hyde,andLivezey,\TheCosmos SystemforDistributedDesignNegotiationSupport"LockheedArticialIntelligence CenterTechnicalReport.1993. 15

[21]Neches,Fikes,Finin,Gruber,Patil,Senator,andSwartout,\Enablingtechnologyfor [22]Patil,Fikes,Patel-Schneider,McKay,Finin,Gruber,andNeches,\TheDARPAKnowledgeSharingEort:Progressreport",InC.Rich,B.Nebel,andW.Swartout(editors), [20J.Fulton.\EnterpriseIntegrationUsingtheSemanticUnicationMeta-Model".EnterpriseIntegrationModeling,C.Petrieed.,MITPress,1992. knowledgesharing",aimagazine,vol.12,no.3,16-36.1991. [23]C.Petrie,\AMinimalistModelforCoordination",ProceedingsofAAAI-92Workshop PrinciplesofKnowledgeRepresentationandReasoning:ProceedingsoftheThirdInternationalConference,Cambridge,MA,MorganKaufmann.1992. [25]Toye,Cutkosky,Leifer,Tenenbaum,andGlicksman,\SHARE:AMethodologyand [24]N.SinghandM.Genesereth,\ImplementationDetailsforAgentBasedSoftwareEngineeringInteroperation",InternalStanfordUniversityLogicGroupTechReport.1992. EnvironmentforCollaborativeProductDevelopment",StanfordCenterforDesign ondesignrationale.toappearinenterprisemodeling,c.petrie(editor),mitpress. [26]J.Weber,B.Livezey,J.McGuire,andR.Pelavin,\Spreadsheet-LikeDesignThrough ResearchTechnicalReport1993-0420. [27]G.Yost,\ConguringElevatorSystems",TechnicalReport,DigitalEquipmentCorporation,111LockeDrive(LMO2/K11),Marlboro,MA,02172.1992. TechnicalModelingSystemsinaKBMSEnvironment",InternationalJournalofSys- [28]S.Dessloch,C.Huebel,N.Mattos,B.Sutter,\HandlingFunctionalConstraintsof searchandapplications,vol5,no.1.1992. Knowledge-BasedToolIntegration",InternationalJournalofExpertSystems:Re- [30]D.Ullman,T.Dietterich,andL.Stauer,\Amodelofthemechanicaldesignprocess [29]E.Subrahmanian,A.Westerberg,G.Podnar,\Towardsasharedinformationenvironmentforengineeringdesign",Computer-AidedCooperativeProductDevelopment MIT-JSMEWorkshop,D.Sriram,R.Logcher,S.Hukuda,eds.,Springer-Verlag,1991. temsautomation:researchandapplications,vol.1no.4,1991. ServiceMail:Underlyinganyknowledgetransportprotocolisaneectivemessagepassing ATechnologyAvailableforDissemination basedonempiricaldata",aiedam,vol.2,no.1,pp.33-52,1988. mail,theshadeprojecthasproducedandisfreelydistributingtheeitservicemail(tm) toprogramsinordertorequestsomeautomatedorsemi-automatedservice.userssend layer.agentsmustbeabletoexchangebits.inrecognitionoftheubiquitousnatureofe- toolkit.thisenablesthecreationofengineeringservices(rendering,layout,etc.)thatare theirrequestsintheheadersand/orbodiesofe-mailmessages,includinganyrelevantdata les.therehavebeenseveralapplicationsalongthislineaccessiblethroughelectronicmail, accessedusingmultimediaelectronicmail.theideaofservicemailisthatofsendinge-mail includingservicesforarchivalsearches,mailinglistmanipulation,conferenceinformation, etc.shadehasexperimentedwithseveralnewapplicationsofservicemail,including: 16

KQMLAPI:ToenableagentstouseKQML,theSHADEprojecthasdenedandimplementedaninitialAPI(applicationprogrammerinterface)throughwhichagentprograms checkplot/millingserviceattheuniv.ofutah. asemiconductorfabricationprocesssimulatorserviceatstanford;andamechanicalpart aseitherstringsor\s-expressions".theapihidesthetransportmediumandcurrently cansendandreceivemessages.theapisupportssendingandreceivingofkqmlmessages supportseithertcp/ipore-mailtransport.theapiiscurrentlyavailableforcandlisp. ingportableontologiesandorganizingknowledgeexpressedinkif.anextensibletranslation OntolinguaandEngineeringMathOntologies:Ontolinguaisasystemformaintain- architectureisprovidedtomaprepresentationlanguagesintoandoutofacanonicalkif Content-BasedRouter/DeductiveDatabaseAgent:ThisagentisaKQML/KIF literaterestrictedrstorderpredicatecalculusengine,capableofupdating,querying,and form.sampleontologies,includingtheengineeringmaththeories,arealsoprovided. monitoringitsinternalmodel.theagentalsomonitorsinter-agentmessagetracandroutes messagestointerestedpartieswhendeductivelydenedinterestcriteriaaresatised. 17