welcome and introduction - ptolemy project · welcome and introduction edward a. lee icyphy mini...
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UniversityofCaliforniaatBerkeley
WelcomeandIntroduction
EdwardA.Lee
iCyPhyMiniWorkshop,Berkeley,Feb.14,2019
Professor of the Graduate School
iCyPhyIndustrialCyber-PhysicalSystemsCenter
Mission:
Tomakeadvancedsoftwareandnetworkingtechnologyusableinsafety-andmission-criticalindustrialapplications.
2 PrabalDutta,EdwardLee,AlbertoSangionvanni-Vincetelli,SanjitSeshia
ActiveProjectPartners
• Avast• Camozzi• Denso• Ford• Siemens• Toyota
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FocusonModels
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Amodelisanydescriptionofasystemthatisnotthething-in-itself.(dasDingansichinKantianphilosophy).
Challenges
• Confusingthemapandtheterritory• Choosingamodelingparadigm• Understandingthepurposeofthemodel
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Solomon Wolf Golomb
Lee,Berkeley 5 Photo by Rusi Mchedlishvili
Youwillneverstrikeoilbydrillingthroughthemap!
Modelsvs.Reality
Inthisexample,themodelinguniverseiscalculusandNewton’slaws.Faithfulnessishowwellthemodelanditstargetmatch
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Themodel
Thetarget(thethingbeingmodeled).
AModel
7 ImagebyDominiqueToussaint,GNUFreeDocumentationLicense,Version1.2orlater.
APhysicalRealization
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• Inscience,thevalueofamodelliesinhowwellitsbehaviormatchesthatofthephysicalsystem.
• Inengineering,thevalueofthephysicalsystemliesinhowwellitsbehaviormatchesthatofthemodel.
Ascientistasks,“CanImakeamodelforthisthing?”Anengineerasks,“CanImakeathingforthismodel?”
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TheValueofModels
ModelFaithfulness
• Toascientist,themodelisflawed.• Toanengineer,therealizationisflawed.
Engineeringismoreaboutmakingthethingmatchthemodelratherthantheotherwayaround.
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ConsiderChipDesign
Apieceofsiliconthatdoesn’tbehavelikethemodelisjustbeachsand.
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IntelHaswell,eachwith1.4billiontransistors
ModelsandModelsandThings
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Models
Things
Science Engineering
Assurance
Hope
Models
Abstraction Refinement
Assurance
UsefulModelsandUsefulThings
“Essentially,allmodelsarewrong,butsomeareuseful.”
Box,G.E.P.andN.R.Draper,1987:EmpiricalModel-BuildingandResponseSurfaces.WileySeriesinProbabilityandStatistics,Wiley.
“Essentially,allsystemimplementations
arewrong,butsomeareuseful.”LeeandSirjani,“Whatgoodaremodels,”FACS2018.
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ChangingtheQuestion
Isthequestionwhetherourmodelsdescribethethinginitself(faithfully)?OrIsthequestionwhetherwecanbuildathing-in-itselfwherebehaviormatchesthatofourmodels(withhighprobability)?
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VerificationandValidation
PerBoehm:• AmIbuildingtheproductright?(verification)• AmIbuildingtherightproduct?(validation)
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VerificationandValidation
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Model
Thing
Yourdesign
Whatyouwant
Model Requirements
Validation:Isthis
faithful?
Verification:Isthisasoundabstraction?
CyberPhysicalSystems
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Whatkindsofmodelsshouldweuse?
SoftwareasaModel
18 Lee,Berkeley
PhysicalSystem Model
Single-threadedimperativeprogramsaredeterministicmodels
PhysicsasaModel
PhysicalSystem Model
Signal Signal
DifferentialEquationsaredeterministicmodels
Lee,Berkeley 19
Image:WikimediaCommons
Signal Signal
20 Image:WikimediaCommonsLee,Berkeley
AmajorproblemforCPS:combinationsofdeterministicmodelsarenondeterministic
OurStrategy
Findengineeringmodelsforwhichwecan:• buildfaithfulrealizations,• verifypropertieswecareabout,and• designinterestingandusefulsystems.
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