ontology engineering
TRANSCRIPT
Ontologyengineering
Valen.naTamma
BasedonslidesbyA.GomezPerez,N.Noy,D.McGuinness,E.Kendal,A.RectorandO.Corcho
Summary
• Stepsofontologydesign– Analysisandrequirements;
– Determinescope;– Considerreuse;– Enumerateterms;
– Defineclasses;
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Extendtheconcepts:“Laddering”• Takeagroupofthingsandaskwhattheyhaveincommon– Thenwhatother‘siblings’theremightbe
• e.g.– Plant,AnimalLivingThing
• MightaddBacteriaandFungibutnotnow
– Cat,Dog,Cow,PersonMammal• OthersmightbeGoat,Sheep,Horse,Rabbit,…
– Cow,Goat,Sheep,HorseHoofedanimal(“Ungulate”)• Whatothersarethere?Dotheydivideamongstthemselves?
– Wild,Domes.cDemoes.ca.on• Whatotherstates–“Feral”(domes.creturnedtowild)
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Choosesomemainaxes
• Addabstrac.onswhereneeded– e.g.“Livingthing”
• iden.fyrela.ons(thisfeedsintothenextstep)– e.g.“eats”,“owns”,“parentof”
• Iden.fydefinablethings– e.g.“child”,“parent”,“Mother”,“Father”
• Thingswhereyoucansayclearlywhatitmeans– Trytodefineadogprecisely–verydifficult
» A“naturalkind”
• makenamesexplicit
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Example
• LivingThing– Animal
• Mammal– Cat– Dog– Cow– Person
• Fish– Carp– Goldfish
– Plant• Tree• Grass• Fruit
• Modifiers– domes.c
• pet• Farmed
– Drac– Food
– Wild– Health
• healthy• sick
– Sex• Male• Female
– Age• Adult• Child
Definable Carinvore Herbivore Child Parent Mother Father Food Animal Draft Animal
Relations eats owns parent-of …
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Iden.fyself‐standingen..es
• Thingsthatcanexistonthereown– People,animals,houses,ac.ons,processes,…
• Roughlynouns
• Modifiers– Thingsthatmodify(“inhere”)inotherthings
• Roughlyadjec.vesandadverbs
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Reorganiseeverythingbut“definable”thingsintopuretrees–thesewillbethe“primi.ves”
• Self_standing– LivingThing
• Animal
– Mammal» Cat» Dog» Cow» Person» Pig
– Fish» Carp
Goldfish
• Plant– Tree– Grass– Fruit
• Modifiers– Domes.ca.on
• Domes.c• Wild
– Use• Drac• Food• pet
– Risk• Dangerous• Safe
– Sex• Male• Female
– Age• Adult• Child
Definables Carnivore Herbivore Child Parent Mother Father Food Animal Draft Animal
Relations eats owns parent-of …
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Commentscanhelptoclarify
• Self_standing– LivingThing
• Animal
– Mammal» Cat» Dog» Cow» Person» Pig
– Fish» Carp
Goldfish
• Plant– Tree– Grass– Fruit
– Abstractancestorconceptincludingalllivingthings–restricttoplantsandanimalsfornow
Classinheritance• Classesareorganizedintosubclass‐superclass(orgeneraliza.on‐
specializa.on)
Hierarchies:• Classesare“is‐a”relatedifaninstanceofthesubclassisan
instanceofthesuperclass– Classesmaybeviewedassets– Subclassesofaclassarecomprisedofasubsetofthesuperset
• Examples– MammalisasubclassofAnimal– Everypenguinisabirdoreveryinstanceofapenguin(likeTweetyisan
instanceofbird
– DracanimalisasubclassofAnimal
Levelsintheclasshierarchy
• Differentmodesofdevelopment–Top‐down‐definethemostgeneralconceptsfirstandthenspecializethem– Bokom‐up‐definethemostspecificconceptsandthenorganizetheminmoregeneralclasses
– Combina.on(typical–breadthatthetoplevelanddepthalongafewbranchestotestdesign)
• ClassinheritanceisTransi.ve–AisasubclassofB–BisasubclassofC–thereforeAisasubclassofC
Levelsintheclasshierarchy
Middlelevel
Toplevel
Bo,omlevel
OntologydesignprocessRequirement
anddomainanalysis
Determinescope
Considerreuse
Enumerateterms
Defineclasses
Defineproper.es
Defineconstraints
AddInstances
Defineproper.es
• Oceninterleavedwiththepreviousstep• Proper.es(orrolesinDL)describetheakributesofthemembersofaclass
• Theseman.csofsubClassOfdemandsthatwheneverAisasubclassofB,everypropertystatementthatholdsforinstancesofBmustalsoapplytoinstancesofA– Itmakessensetoakachproper.estothehighestclassinthehierarchytowhichtheyapply
Defineproper.es
• Typesofproper.es–“intrinsic”proper.es:flavorandcolorofwine–“extrinsic”proper.es:nameandpriceofwine–parts:ingredientsinadish–rela.onstootherobjects:producerofwine(winery)
• Theyarerepresentedbydataandobjectproper.es–simple(datatype)containprimi.vevalues(strings,numbers)–complexproper.escontainotherobjects(e.g.,awineryinstance)
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Modifiersandrela.ons
• Modifiers– Domes.ca.on
• Domes.c• Wild
– Use• Drac• Food• pet
– Risk• Dangerous• Safe
– Sex• Male• Female
– Age• Adult• Child
Relations eats owns parent-of …
OntologydesignprocessRequirement
anddomainanalysis
Determinescope
Considerreuse
Enumerateterms
Defineclasses
Defineproper.es
Defineconstraints
AddInstances
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Iden.fythedomainandrangeconstraintsforproper.es
• AnimaleatsLiving_thing– eatsdomain:Animal;
range:Living_thing
• PersonownsLiving_thingexceptperson– ownsdomain:Person
range:Living_thing¬Person
• Living_thingparent_ofLiving_thing– parent_of:domain:Living_thing
range:Living_thing
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Ifanythingisusedinaspecialway,addatextcomment
• AnimaleatsLiving_thing– eatsdomain:Animal;
range:Living_thing
— ignoredifferencebetweenpartsoflivingthingsandlivingthingsalsoderivedfromlivingthings
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Fordefinablethings• Paraphraseandformalisethedefini.onsintermsofthe
primi.ves,rela.onsandotherdefinables.
• Noteanyassump.onstoberepresentedelsewhere.
– Addascommentswhenimplemen.ng
• “A‘Parent’isananimalthatistheparentofsomeotheranimal”(Ignoreplantsfornow)– Parent=
Animalandparent_ofsomeAnimal
• “A‘Herbivore’isananimalthateatsonlyplants”(NBAllanimalseatsomelivingthing)– Herbivore=
AnimalandeatsonlyPlant
• “An‘omnivore’isananimalthateatsbothplantsandanimals”– Omnivore=
AnimalandeatssomeAnimalandeatssomePlant
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Whichproper.escanbefilledinattheclasslevelnow?
• Whatcanwesayaboutallmembersofaclass?– eats
• Allcowseatsomeplants• Allcatseatsomeanimals
• Allpigseatsomeanimals&eatsomeplants
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Fillinthedetails(canusepropertymatrixwizard)
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Checkwithclassifier
• CowsshouldbeHerbivores– Arethey?whynot?
• Whathavewesaid?– Cowsareanimalsand,amongstotherthings,eatsomegrassandeatsomeleafy_plants
• Whatdoweneedtosay:Closureaxiom
– Cowsareanimalsand,amongstotherthings,eatsomeplantsandeatonlyplants
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ClosureAxiom
Cowsareanimalsand,amongstotherthings,eatsomeplantsandeatonlyplants
Closure Axiom
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Inthetool
• Rightmousebukonshortcutforclosureaxioms
– foranyexisten.alrestric.on
addsclosureaxiom
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OpenvsClosedWorldreasoning
• Openworldreasoning– Nega.onascontradic.on
• Anythingmightbetrueunlessitcanbeprovenfalse– Reasoningaboutanyworldconsistentwiththisone
• Closedworldreasoning– Nega.onasfailure
• Anythingthatcannotbefoundisfalse– Reasoningaboutthisworld
• Ontologiesarenotdatabases
OntologydesignprocessRequirement
anddomainanalysis
Determinescope
Considerreuse
Enumerateterms
Defineclasses
Defineproper.es
Defineconstraints
AddInstances
Crea.nginstances
• Createaninstanceofaclass– Theclassbecomesadirecttypeoftheinstance– Anysuperclassofthedirecttypeisatypeoftheinstance
• Assignslotvaluesfortheinstanceframe– Slotvaluesshouldconformtothefacetconstraints– Knowledge‐acquisi.ontoolsocencheckthatconstraintsaresa.sfied
Crea.nginstances
• Fillingtheontologieswithsuchinstancesisaseparatestep
• Numberofinstances>>numberofclasses
• Thuspopula.nganontologywithinstancesisnotdonemanually– Retrievedfromlegacydatasources(DBs)
– Extractedautoma.callyfromatextcorpus
OntologydesignprocessRequirement
anddomainanalysis
Determinescope
Considerreuse
Enumerateterms
Defineclasses
Defineproper.es
Defineconstraints
AddInstances
Summary
• Stepsofontologydesign– Defineclasses;– Defineproper.es;– Defineconstraints;– Defineinstances;– Considerthestepsalloveragain…