Ontology engineering
30
Ontology engineering Valen.na Tamma Based on slides by A. Gomez Perez, N. Noy, D. McGuinness, E. Kendal, A. Rector and O. Corcho
Transcript of Ontology engineering
Ontologyengineering
Valen.naTamma
BasedonslidesbyA.GomezPerez,N.Noy,D.McGuinness,E.Kendal,A.RectorandO.Corcho
Summary
• Stepsofontologydesign– Analysisandrequirements;
– Determinescope;– Considerreuse;– Enumerateterms;
– Defineclasses;
53
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)
54
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
55
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 …
56
Iden.fyself‐standingen..es
• Thingsthatcanexistonthereown– People,animals,houses,ac.ons,processes,…
• Roughlynouns
• Modifiers– Thingsthatmodify(“inhere”)inotherthings
• Roughlyadjec.vesandadverbs
57
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 …
58
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)
65
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
67
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
68
Ifanythingisusedinaspecialway,addatextcomment
• AnimaleatsLiving_thing– eatsdomain:Animal;
range:Living_thing
— ignoredifferencebetweenpartsoflivingthingsandlivingthingsalsoderivedfromlivingthings
69
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
70
Whichproper.escanbefilledinattheclasslevelnow?
• Whatcanwesayaboutallmembersofaclass?– eats
• Allcowseatsomeplants• Allcatseatsomeanimals
• Allpigseatsomeanimals&eatsomeplants
71
Fillinthedetails(canusepropertymatrixwizard)
72
Checkwithclassifier
• CowsshouldbeHerbivores– Arethey?whynot?
• Whathavewesaid?– Cowsareanimalsand,amongstotherthings,eatsomegrassandeatsomeleafy_plants
• Whatdoweneedtosay:Closureaxiom
– Cowsareanimalsand,amongstotherthings,eatsomeplantsandeatonlyplants
73
ClosureAxiom
Cowsareanimalsand,amongstotherthings,eatsomeplantsandeatonlyplants
Closure Axiom
74
Inthetool
• Rightmousebukonshortcutforclosureaxioms
– foranyexisten.alrestric.on
addsclosureaxiom
75
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…
