temporality in semantic web - graduate center, cuny...schema.org • schema.org was created in 2011...
TRANSCRIPT
![Page 1: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/1.jpg)
TemporalityinSemanticWeb
Ph.D student:DiWu,GraduateCenter,CUNYMentor:AbdullahUz Tansel,BaruchCollege,CUNY
Committee:SarahZelikovitz,CIS,CUNYSusanP.Imberman,CIS,CUNY
![Page 2: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/2.jpg)
Abstract• SemanticWeb• SemanticWebTechnologies• TimeOntology• TemporalDatabase• TemporalRelationalAlgebra• ResearchDirection
![Page 3: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/3.jpg)
Motivation• Data• Centralized• Distributed• Decentralized
• Moredata• SemanticWeb
• Betterdata• Accurate• UptoDate• Historicaldata
![Page 4: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/4.jpg)
SemanticWeb• Definitionisdevelopedin1960s.• anextensionofthecurrentWWW.• informationiswell-definedwithmeaning.• enablecomputers andpeopletounderstand.
• DataissavedovertheWWW:• Rowsharing:entity-basedview• Columnsharing:attribute-basedview• Cellsharing:SemanticWeb,RDFview
![Page 5: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/5.jpg)
SemanticWeb- Success• Over2.5billionwebpageshavemarkupconformingtotheschema.org format;• LinkeddataiswidelyadoptedbymajorlibrariesandmuseumsaswellasmediasitessuchasBBCandNewYorkTimes;• WebcompaniesaredevelopingknowledgegraphsthatlinkmassivenumberofentitiestogethersuchasGoogle,Bing,andFacebook;• CommercialdatabasesystemsareprovidingnativesupportforSemanticWeblanguagessuchasOracle;• Recommendercompaniesaretakingadvantageofsemanticsandtaggingtoimprovetheiraccuracy;• Theworldhealthorganizationisdevelopingthemaininternationalterminologyfordiseasesasanontologyforsemanticwebusers;etc.
![Page 6: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/6.jpg)
SemanticWeb- Challenges• ThedevelopmentisstillbelowtheexpectationsofthefoundersoftheSemanticWeb.• Westillhavefewmeanstoeasilygeneratesemanticwebannotations.• Itischallengingthathowtoeffectivelyqueryhugenumberofdecentralizedinformationrepositoriesofvaryingscales.• TheresearchofSemanticWebhastransitionedintolarger,moreappliedsystems.• AlthoughcurrentSemanticWebimplementationssupportsometemporalelements,however,itisnotenoughtosolvetheproblem“Findingaccuratecurrentdata”.
![Page 7: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/7.jpg)
Ontology• Anontologyisanexplicitspecificationofaconceptualization- thetermsinthedomainandtherelationshipamongthem.• Itdefinesacommonlyacceptedvocabularyforadomainforinformationsharing- notonlyhumanbeingsbutalsomachineagents.• Themainrequirementsforagoodontologyincludewell-definedsyntax,efficientsupportforreasoning,aclearandformalsemantics,sufficientpowerofexpression,andeasytoexpress.• AgoodontologyforTimeiscriticalandfundamental.
7
![Page 8: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/8.jpg)
OntologyGuide• Thereare7stepstodevelopanontology:• Step1:Domainandscope• Step2:Reuseexistingontologies• Step3:Definingimportantterms• Step4:Definingclassesandclasshierarchy• Step5:Definingpropertiesofconcepts• Step6: Definingfacetsofproperties• Step7: Fillvaluetocreateaninstance
8
![Page 9: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/9.jpg)
DescriptionLogic• DescriptionLogiciswidelyusedinontologicalmodeling.DescriptionLogicOntologiesconsistofasetofstatements,whicharecalledaxiomsthatmustbetrue.• Assertionalaxioms(ABox)• Representsattributesorfactsoftheobject
• Terminologicalaxioms(TBox)• Representrelationshipsbetweenconcepts
• Relationalaxioms(RBox)• Representthepropertyofroles
9
![Page 10: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/10.jpg)
DLNotations
10
![Page 11: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/11.jpg)
ResourceDescriptionFramework• TraditionalRelationalDatabaserepresentsinformationeitherbyColumn(forspecifictopics)orbyRow(forsomeentities).• RDFmakesinformationrepresentedbyCell(apieceofinformation)possible.• TheRDFdatamodelisbasedasetofstatements,whicharesubject-predicate-objecttriples.• Thesubjectinthetriplerepresentsaresource.• Thepredicaterepresentstherelationshipbetweenthesubjectandtheobject.• Theobjectrepresentsattributesorpropertiesoftheresource.
![Page 12: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/12.jpg)
RDF-Statement
12
![Page 13: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/13.jpg)
RDF-CodePseudo code:<rdf:Description rdf:about="Subject">
<Predicate rdf:resouces="Object"></Predicate><Predicate>Literal</Predicate>
</rdf:Description>
<?xml version="1.0"?><rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:ex="http://example.org/"><rdf:Description rdf:about="http://www.example.org/WWeber">
<ex:livesIn rdf:resouces="http://www.example.org/NewYorkCity"></ex::livesIn><ex:fullName>William Weber</ex::fullName>
</rdf:Description>
</rdf:RDF>
13
![Page 14: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/14.jpg)
RDFa• RDFa(ResourceDescriptionFrameworkinAttributes)isaW3CRecommendationthataddsasetofattributelevelextensionstoHTMLandvariousXML-baseddocumenttypesforembeddingmetadata.
<p author ="http://www.example.org/people" >William Weber<span property = "http://www.example.org/livesIn"> lives in</span><span location = "http://www.example.org/location"> New York City</span>
</p>
14
![Page 15: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/15.jpg)
Turtle• AturtledocumentenablesrepresentingaRDFgraphinacompacttextualformat.• BesidethenamespacedefinitionsaswehaveseeninRDF,turtleisverycompactbecauseoftheuseofcolumntolistpredicates,andcomatolistobjects.
15
![Page 16: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/16.jpg)
N-Triple• N-TriplescorrespondsdirectlytotherawRDFtriplesandusesfullyunabbreviatedURIs.Thesubject,predicateandobjectofanRDFTriplearerepresentedinasequenceandseparatedbywhitespace.Thissequenceisterminatedbya’.’andanewline.
<http://one.example/subject1> <http://one.example/predicate1><http://one.example/object1> . # comments here
# or on a line by themselves_:subject1 <http://an.example/predicate1> "object1" ._:subject2 <http://an.example/predicate2> "object2" .
16
![Page 17: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/17.jpg)
Notation3• Notation3(N3)isamorecompactserializationofRDF.Namespacesareusedtoabbreviatethestatements.Thus,N3providesacompactrepresentation.SimilartoTurtle,‘;’isusedtoindicateanothertriplewiththesamesubject,and‘,’isusedtoseparateobjects.
17
![Page 18: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/18.jpg)
Reification• Reification,isusingabuilt-invocabularyinRDFfordescribingstatementssothatweknowmorethanthemerelybinaryrelationship,or,inotherwords,ismakingstatementsaboutotherstatements.
• Inpractice,Reificationalwaysusesfourstatementsfordescribingstatements,andthusiscalled“reificationquad”.
• Thestandardreificationhasbeencriticizedforitslackofefficiency:• SingletonProperty:createsnewpropertythatembedsboththeoriginalandadditionalproperty
• N-aryrelations:createsanintermediateresourcetodenotetherelationship.
18
![Page 19: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/19.jpg)
WebOntologyLanguage• OWLisalogic-basedlanguage,andmachineagentsareabletoexploitknowledgeexpressedinOWL.• TheW3CWebOntologyLanguageisalsoaSemanticWeblanguage.Itisdesignedtoexpressrichinformation.• OWL2asthemostcurrentversionwasreleasedin2012byW3Crecommendation.• TheOWL2ontologyprovidesstructuresasclasses,properties,individuals,anddatavalues,andarestoredasSemanticWebdocuments.
19
![Page 20: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/20.jpg)
LinkedDataInitiative• LinkedDataInitiativeispartoftheSemanticWebinthewaythatresourcesoverthewebofhypertextcanbelinkedsohumanandmachineagentscanreachouttomoredataiftheyhavesome.
• ThefourprinciplesoflinkeddataasTimBerners-Leeproposedare:1)UseURIsasnamesforthings;2)UseHTTPURIssothatpeoplecanlookupthosenames;3)WhensomeonelooksupaURI,provideusefulinformation,using
thestandardsRDF,SPARQL);4)IncludelinkstootherURIssothattheycandiscovermorethings.
20
![Page 21: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/21.jpg)
DublinCoreMetadataInitiative• TheDublinCoreMetadataInitiativeisoneofRDFvocabularythathasametadataelementandinthebeginningitprovidespropertiessuchascreator,publisher,andtitle,etc.• Thisoriginal15metadataelementsaredefinedevenbeforeRDFsothattheyhaveaseparatenamespace.• NowadaysDCMIisoneofthemostpopularRDFvocabulariesanditisinlinewiththeLinkedDatamovement.• SimpleDublinCorehas24elementswhileQualifiedDublinCorehas3additionalelements.
21
![Page 22: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/22.jpg)
FOAF• AsFOAFstandsforFriendofaFriend,FOAFusesRDFtechnologytoconnectinformationonaperson’shomepagewiththatofhis/herfriends,andthefriendsofhis/herfriends.
• FOAFenablesmachinestounderstandapage,andlearnrelationsthatconnectpeople,places,andthingsontheweb.
• FOAFcangreatlyexpandtheknowledgebaseofwebasawhole.
• FOAFisveryeasytouseandtherearevariousFOAFtoolsforgeneratingFOAFfilessuchasFOAFsite,foaf-a-matic,etc
22
![Page 23: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/23.jpg)
GoogleKnowledgeGraph• TheKnowledgeGraphisaknowledgebaseofGoogletoimproveitssearchengineandenhancetheresultbyaddingadisplayofstructuredanddetailedinformationbesidesthetraditionallistoflinkstoothersites.
• TheKnowledgeGraphprovidesaconvenientwayforGoogle’ssearchengineusersthattheydon’tneedtogofurtherforinformationiftheyaresatisfiedwiththeKnowledgeGraphdisplay.
• GoogleNowexploitstheresultoftheKnowledgeGraphandusestheshortsummaryforthekeywords/topicasfeedbacktoitsusers.
• TheKnowledgeGraphtakesasemanticsearchfromvarioussourcesincludeWikidataandWikipediaetc.
23
![Page 24: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/24.jpg)
Schema.org• Schema.orgwascreatedin2011bymajorsearchenginesBing,Google,andYahoo.• Itaimsatprovidingasingleschemathatcoversawiderangeoftopics.Whilewebmastersonlyneedtowiththemarkuponce,searchenginescanusethemarkupdifferently.• TheideaofSchema.orgactuallyalignwithRDFthatapieceofinformationisrepresentedasatriplebydataprovidesandhowtoretrievetheinformationistheworkofquerydevelopers.
24
![Page 25: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/25.jpg)
LinkedOpenVocabularies• Basedontheviewofvocabulariesalsodata,thenameLinkedOpenVocabulariesisderivedfromLinkedOpenData.• LOVprovidesachoiceofmanyvocabulariesbasedonasetofcriteriasuchasURIstabilityandavailability,properversion,etc.• MostoftheestablishedvocabulariesarecollectedinLOV,aswellastheirversionhistoryandrelationshipsamongeachother.• LOVprovidesatoolforwebmasterstochoosebestvocabularywithlessconsiderations.
25
![Page 26: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/26.jpg)
Timeontology• Timeisoneofthemostimportantconceptinmostscientificfields.Manyculturesregardtimeandspaceasthefundamentalscaleoftheworld.• TemporalEntity• TemporalRule• TemporalConcepts• TemporalFeature• TemporalProperMeasure
26
![Page 27: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/27.jpg)
Timeontology• Atemporalelementistheprimitiveentitythatisusedtorepresenttime.TheseelementsforatheoryoftimeareTimePointsandTimeIntervals.• TimePointsaretheelementsofatimelinewhichcanalsobecalledinstants.Timepoint(instant)thasnoduration.Thevalueoftdiffersinthespecificprograms.Someassignnonnegativevaluestoaninstant,someassignnegativevaluetorepresentpastandpositivetorepresentfuture.
• TimeIntervalsareusedtoextendthepoint-basedmodeloftimetorepresentaperiodorapartofthetime.Also,therelationship“during"isassociatedwithaduration,whichcannotbetimepoints,butbeaninterval.Sometheoriesarguethattimeintervalisacompoundstructureoftimepoints.
27
![Page 28: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/28.jpg)
TemporalProperties• DatesandTimestampsbotharewidelyusedinprograms.• Datesareorderedtriplesofintegersforyear,month,andday.• Timestampscouldbeinterpretedasametricreferencetoapointinthetime
line.Timestampscancontainpreciseinformationandtheprecisenessisdependedonthesystem.
28
![Page 29: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/29.jpg)
TemporalRelations• TemporalRelationsarethebinarypropertiesamongelementsofatimemodel.Dependsontheelementsintherelationship,therearethreecategories:pointtopoint,pointtointerval,andintervaltointerval.
29
![Page 30: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/30.jpg)
Temporaldatabase• AValidTimeisatimeperiodduringwhichthestatement/recordistruewithrespecttotherealworld.Thetemporalattributesforvalidtimeareindependentofthetransactiontimeinthedatabase;theyarereflectingthetimeinrealworld.• ATransactionTimeisatimeperiodduringwhichthestatement/recordinthedatabaseisconsideredtobetrue.Itisassociatedwiththetimethatthestatementisaddedtothedatabaseandisassumetobetruetillnow.
30
![Page 31: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/31.jpg)
HistoricalDatabase• Historicaldatabaseonlysupportsvalidtime.Thus,itcanberegardedasclassicalrelationaldatabasewithanewtemporalattributerepresentsthevalidtime.• Historicaldatabaserepresentsthefulllife-spanofanentitynotjustcurrentstate.Wecanhavedataalreadyexpired(paststate)andwillbevalidinthefuture(futurestate)
31
![Page 32: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/32.jpg)
RollbackDatabase• Rollbackdatabaseistheanothertypeofdatabase.Itisdifferentthanthehistoricaldatabaseandonlysupportstransactiontime.• Rollbackdatabasekeepsallrecordswiththeirtimestampswhentheyareentered.• Rollbackdatabaseisideallyfordatarecoveryfromafailure.
32
![Page 33: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/33.jpg)
Bi-temporalDatabase• Bi-temporaldatabaseisthemostusedtemporaldatabaseinreality.Thisdatabasesupportsbothtypesoftime.
33
![Page 34: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/34.jpg)
TupleTime-stamping• Therearetwoapproachesfortime-stampinginDBMS.Oneistupletimestamping,theotherisattributetime-stamping.• Tupletimestampingapproachkeepsthe1NFrelations,andaddstimestampstoeachtupleinarelation.• Eachtimeweupdateanattributeassociatedwithtime,wehavetoinserta
newtupleintothetable,whichwillproducealotofredundantinformation.• Theadvantageoftupletimestampingisminimumchangeneededforexisting
relationdatabase.
34
![Page 35: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/35.jpg)
AttributeTime-stamping• Attributetimestampingusesamorecomplexwaytostorethetemporalelements.• Whenanattributehasatemporalelements,itwillbeattachedonto,no
mattertheelementsaretimepoints,intervals,etc.• Insteadofasimpleattribute,itbecomesarelationthatexpressesthe
attributevaluewithassociatedtemporalelements.• Thus,attributetime-stampingalsocallednestedtimestamping,becausewe
canconsiderthetemporalattributeasasub-relationofthetuplerelations.
35
![Page 36: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/36.jpg)
TemporalAlgebra• Historicalrelationalalgebra(HRA)• Temporalelementsrepresentvalidtime
• NestedBi-temporalalgebra(NBtA)• Temporalelementsrepresentbothvalidandtransactiontime
36
![Page 37: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/37.jpg)
HRA- Time• Timeisacontinuesvariable;• Indatabases,timeisrecordedasdiscretepoints;• Iftheoriginoftimeist0andcurrenttimeistnow,timeTcanberepresentedasasetof{t0,t1,t2...,tnow },wheret0 <t1 <...<tnow,t0 +1=t1,…,tnow-1+1=tnow.
37
![Page 38: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/38.jpg)
HRA- PointandInterval• Timepointsandintervalsbothrepresenttimevariable;• Theycanbeconvertedintoeachother.• Timepointscanberegardedasthesmallestinterval;• andtimeintervalcanberegardedasasetoftimepoints.• Weuse[l,u)torepresenttheintervalthatstartsattl (lowerbound)inclusiveandendsattu (upperbound)exclusive.• Sinceintervalrepresentationcansavemorespace,wejustuseintervalrepresentationfromnowon.
38
![Page 39: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/39.jpg)
HRA- Attribute• Anattributemayhavetemporalelement.• IftheattributeAistimeinvariant,suchasSocialSecurityNumber,thevalueitselfformsanatom.• IfAistimevariant,thatmeansthevalueaofAisvalidforacertaintimeandnotvalidforothertime,theattributeneedstoincludethetemporalelementas〈[l,u),a〉.
39
![Page 40: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/40.jpg)
HRA- AttributeType• TherearefourtypesofattributesinR.• AtomicattributescontainatomicvalueswhicharesubsetsofU.• Triplet-valuedattributescontaintripletsastheformatof〈[l,u),a〉.• Set-valuedattributescontainsasetofatomicvalues• set-triplet-valuedattributescontainsetsoftripletsasvalues.Eachsetcontains
oneormoretripletsandrepresentsthehistoryoftheattributeoverT.
40
![Page 41: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/41.jpg)
HRA- AttributeType
41
![Page 42: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/42.jpg)
HRA- Basicoperations• StandardrelationalalgebraoperationscanbeappliedtoHistoricalRelationsdirectlywithminormodifications.• Projection(π)andCartesianproduct(×)operationsareremainunchanged.• Setunion (∪)andSetdifference(−)mayhaveoverlapping,adjacent,and
containedintervalsandthenchangetheattributetypefromtriplet-valuedtoset-triplet-valued.
42
![Page 43: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/43.jpg)
HRA- Newoperations• Triplet-valuedattributescanbepackedtoaset-triplet-valuedattributesandunpackdoesthereverse.• Atomicattributescanformtriplet-valuedattributesbytriplet-formationtoconvertthreeattributestogetherwhiletriplet-decompositionbreaktriplet-valuedattributestoitscomponents.• Sliceoperationrestrictsthetimeofanattributebasedonthetimeofanotherattribute.• Drop-timeoperationdiscardsthetimecomponentandonlykeeptheatomoratomsetfromtriplet-valuedattributesorset-triplet-valuedattributes.
43
![Page 44: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/44.jpg)
NBtA - Operations• Thereareeightbasicoperationsin:SetOperations,Projection,Selection,CartesianProduct,Unnest,Nest,TemporalAtomDecomposition,andTemporalAtomFormation.• WhileSetOperation,Projection,CartesianProductareexactlythesameasrelationalalgebra,othersneedmodifications.• Thenestedtemporalmodelisageneralizedmodelofthehistoricalrelationalmodelwherethelatteronehasorder1.• Thus,thealgebraoperationsremainthesameexceptthenestingandunnestingoperations.
44
![Page 45: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/45.jpg)
NBtA - Atoms• BitemporalAtomAbitemporalatomhastwotemporalintervalstorepresentnotonlythevalidtimeofthedatavaluebutalsothetransactiontimeofit.
• Thus,tinabitemporalrelationhasaformatas〈TT,VT,V〉.• Also,sincetimepointsandtimeintervalscanbeconvertedfromonetotheothereasily;andtimeintervalismoregeneral,westillusetimeintervaltorepresentthetransactiontimeandvalidtimeinabitemporalatomas〈[TTl ,TTu),[VTl,VTu),V〉.
45
![Page 46: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/46.jpg)
NBtA - Unnesting• Theunnestingoperationmakesanestedrelationflatten.• IfattributeAofabitemporalrelationRisasetofatomsorbitemporalatoms,
applyingμ toAwillcreateanewtupleforeachatomorbitemporalatominthesetofA,andkeepotherattributesunchanged.
• Ifμ isappliedtoeverybitemporalset-valuedattributeinRrecursively,thenthefinalresultwillbeaflatrelation(1NF)withonlyatomsorbitemporalatoms,ornestingorderof0.
46
![Page 47: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/47.jpg)
NBtA - Nesting• Nestingoperationpacksabitemporalschematomakeitmorecompact.• Ifcertainconditionsaresatisfied,nestingoperationscanreverseazeroorderflattenedbitemporalschemagetfromanestedbitemporalschemausingunnestingoperation.
47
![Page 48: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/48.jpg)
NBtA - Slice• Sliceoperationmodifiesthekth attribute’sbitemporaltimecomponentbasedonthetemporalcomponentofthepth attributebytheoperatorθ∈ {∪,∩,−}.Theresultmaynotbeempty.• The∩representsthe“where”predicateinqueries.
48
![Page 49: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/49.jpg)
NBtA - Decomposition• Bitemporalatomdecompositionoperatorsplitsthekth attributesAofrelationRintofivenewattributesthatwereit’scomponents:A.TTl ,A.TTu,A.VTl ,A.VTu,A.V.
49
![Page 50: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/50.jpg)
NBtA - Formation• Bitemporalatomformationisthereverseofbitemporalatomdecomposition(δ).Itcombinesexistingattributestogethertobuildabitemporalatom.
50
![Page 51: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/51.jpg)
NBtA - Rollback• LetRbeabitemporalrelationschema,<r(1),...r(n)>,wherer(k)isabitemporalattribute.• TheresultcontainsbitemporalatomssuchthatitsTTcomponentincludesthetimet.• Ifwewanttocutthetransactiontimeofthesebitemporalatomssothatyonlyincludestimet,thenwecanreplaceintheaboveformulaz=xbyz=<[t,t+1),x.TT,x.V>.
51
![Page 52: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/52.jpg)
ConnectionandFuture• TemporalelementsincurrentSemanticWebTechnologies• HowtomakesemanticwebmoreexpressivebyborrowingfromTemporalDatabase?• Howtodesignqueriesanddatastructuresothatsearchingresultismoreaccurateandefficient?
52
![Page 53: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/53.jpg)
Q&A
![Page 54: Temporality in Semantic Web - Graduate Center, CUNY...Schema.org • Schema.org was created in 2011 by major search engines Bing, Google, and Yahoo. • It aims at providing a single](https://reader034.vdocument.in/reader034/viewer/2022050305/5f6dff5a44c90c141448431a/html5/thumbnails/54.jpg)
Thankyou