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1、Chapter4Modelsofgeospatialinformation©WorboysandDuckham(2004)GIS:AComputingPerspective,SecondEdition,CRCPress©WorboysandDuckham(2004)GIS:AComputingPerspective,SecondEdition,CRCPressOntology:thestudyofgeneralclassificationsof,andrelationshipsbetween,thoseth
2、ingsthatexistintheworldAbasicontologicaldistinctionisthedivisionoftheworldintoentitiesthathaveidentities(objects)andentitiesthatoccurintime(events)Objectsorcontinuants,maybecategorizedassubstances,partsofsubstances,aggregatesofsubstances,locationsforsubsta
3、nces,andpropertiesofsubstancesTheEarthconstitutesasubstance;thesurfaceoftheEarthispartoftheEarth;thesolarsystemisanaggregateofplanets;theUSAisalocation;andtheEarth’stotallandareaisapropertyoftheEarthOntology©WorboysandDuckham(2004)GIS:AComputingPerspective
4、,SecondEdition,CRCPressModelingWeareinterestedinmodelingpartsofthegeographicworldAnunderstandingofbasicontologicaldistinctionscanhelpusavoidsomebasicmodelingmistakessuchas:Failingtodistinguishreal-worldentitiesfrominformationsystementitiesFailingtodistingu
5、ishsubstancesfromtheirpropertiesAforest,thelocationoftheforest,andtheland-covertype“forested”fallindistinctontologicalcategoriesExample©WorboysandDuckham(2004)GIS:AComputingPerspective,SecondEdition,CRCPressOntologyvs.ModelingKeydistinctions:Ontologyaimsto
6、developgeneraltaxonomiesofwhatexistsDatamodelingaimstodevelopclassificationswithinaparticularapplicationdomainExamples:ThedistinctionbetweensubstanceandpropertyisnotadatamodelingissueThedecisiontorepresentaroadinanavigationsystemasapolylineorasanareaisadat
7、amodelingquestion©WorboysandDuckham(2004)GIS:AComputingPerspective,SecondEdition,CRCPressModelsModel:anartificialconstructioninwhichpartsofonedomain,thesourcedomain,arerepresentedinanotherdomain,thetargetdomainPurposeistosimplifyandabstractawayfromthesourc
8、edomainConstituentsofthesourcedomainaretranslatedbythemodelintothetargetdomainInsight,resultsandcomputationsinthetargetdomainmaythenbeinterpretedinthesourcedomain.Usefulnessisdeterminedbyhowcloselythemodelcan
