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Learning the Semantics of Structured Data Sources

The document discusses the automation of semantic modeling for structured data sources, highlighting the need for explicit semantics that is often absent. It presents a graph-based approach to infer relationships and build semantic models, utilizing known models and ontologies to improve the accuracy and efficiency of the process. The research introduces methods for semi-automatic building, learning semantic types, and inferring relationships, focusing on enhancing user interaction and minimizing refinement efforts.

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Learning the Semantics of Structured Data Sources Mohsen Taheriyan
Motivation 2 How to express the intended meaning of data? Explicit semantics is missing in many of the structured sources name date city state workplace 1 Fred Collins Oct 1959 Seattle WA Microsoft 2 Tina Peterson May 1980 New York NY Google Employee? CEO? Birth date? Death date? Employment date? Person? Organization? Birth city? Work city?
Semantic Model Map the source to the classes & properties in an ontology object property data property subClassOf Person Organization Place Stat e name birthdate bornIn worksFor state name phone name livesIn City Event ceo location organizer nearby startDate title isPartOf postalCode 3 name date city state workplace 1 Fred Collins Oct 1959 Seattle WA Microsoft 2 Tina Peterson May 1980 New York NY Google SourceDomainOntology
Semantic Types Person OrganizationCity State name birthdate name namename 4 Person name date city state workplace 1 Fred Collins Oct 1959 Seattle WA Microsoft 2 Tina Peterson May 1980 New York NY Google
Relationships OrganizationCity State name birthdate name namename 5 Person name date city state workplace 1 Fred Collins Oct 1959 Seattle WA Microsoft 2 Tina Peterson May 1980 New York NY Google bornIn worksFor state
Problem: How to automate building semantic models for structured sources?
Outline • Semi-automatically building semantic models • Learning semantics models from known models • Inferring semantic relations from LOD • Related Work • Discussion & Future Work 8
Semi-automatically Building Semantic Models Contribution: a graph-based approach to extract implicit relationships
Approach [Knoblock et al, ESWC 2012] 10 Domain Ontology Learn Semantic Types Extract Relationships Steiner Tree Sample Data Construct a Graph Implemented in Karma http://www.isi.edu/integration/karma @KarmaSemWe b
Example Source object property data property subClassOf Domain Ontology 12 name date city state workplace 1 Fred Collins Oct 1959 Seattle WA Microsoft 2 Tina Peterson May 1980 New York NY Google Goal: Find a semantic model for the source (map the source to the ontology)
Learning Semantic Types [Krishnamurthy et al., ESWC 2015] 13 class? property ? workplace Google Microsoft Amazon …
Learning Semantic Types 14 Organization name workplace Google Microsoft Amazon … 1. User Specifies 2. Systems learns
Learning Semantic Types 15 Organization name workplace Google Microsoft Amazon … employer Facebook Apple Google …
Learning Semantic Types 16 Organization name workplace Google Microsoft Amazon … Organization name employer Facebook Apple Google …
Semantic Labeling Approach • Each semantic type: label • Each data column: document • Textual Data – Compute TF/IDF vectors for documents – Compare documents using Cosine Similarity between TF/IDF vectors • Numeric Data – Use Statistical Hypothesis Testing – Intuition: distribution of values in different semantic types is different, e.g., temperature vs. population • Return Top-k suggestions based on the confidence scores 17
Construct a Graph Construct a graph from semantic types and ontology 18 Person OrganizationCity State name birthdate name namename Person name date city state workplace 1 Fred Collins Oct 1959 Seattle WA Microsoft 2 Tina Peterson May 1980 New York NY Google
Construct a Graph Construct a graph from semantic types and ontology date 19
Inferring the Relationships Select minimal tree that connects all semantic types – A customized Steiner tree algorithm 22 date
Result in Karma 23
Refining the Model 24 Impose constraints on Steiner Tree Algorithm – Change weight of selected links to ε – Add source and target of selected link to Steiner nodes date
Final Semantic Model 25
Evaluation 26 Evaluation Dataset EDM # sources 29 # classes in the ontologies 119 # properties in the ontologies 351 # nodes in the gold standard models 473 # links in the gold standard models 444 • Measured the user effort in Karma to model the sources • Started with no training data • User actions – Assign/Change semantic types – Change relationships
User Effort 27 source columns Choose Type Change Link Time (min) s1 7 7 1 3 s2 12 5 2 6 s3 4 0 0 2 s4 17 5 7 8 s5 14 4 6 7 s6 18 4 4 7 s7 14 1 4 6 s8 6 0 4 3 … … … … … s29 9 2 1 3 Total 329 56 96 128 Avg. min per source: 4.4 minutes Avg. # user actions per source: 152/29=5.2
Limitation • This approach does not learn the changes done by the user in relationships • User has to go through the refinement process each time 28
Learning Semantic Models Contribution: exploiting known semantic models to learn relationships
Main Idea 30 Sources in the same domain often have similar data Exploit knowledge of known semantic models to hypothesize a semantic model for a new sources
Example 31 EDM SKOS FOAF AAC ElementsGr2ORE DCTermsDomain ontologies: Source: Dallas Museum of Art  dma(title,creationDate,name,type) Domain: Museum Data
Example 32 EDM SKOS FOAF AAC ElementsGr2ORE DCTermsDomain ontologies: Domain: Museum Data Source: National Portrait Gallery  npg(name,artist,year,image)
Example 33 EDM SKOS FOAF AAC ElementsGr2ORE DCTermsDomain ontologies: Domain: Museum Data Goal: Automatically suggest a semantic model for dia Source: Detroit Institute of Art  dia(title,credit,classification,name,imageURL)
Approach [Taheriyan et al, ISWC 2013, ICSC 2014, JWS 2015] Domain Ontology Learn Semantic Types 34 Sample Data Construct a Graph Generate Candidate Models Rank Results Known Semantic Models Implemented in Karma
Approach 36 Input Learn semantic types for attributes(s) • Sample data from new source (S) • Domain Ontologies (O) • Known semantic models Construct Graph G=(V,E) Generate mappings between attributes(S) and V Generate and rank semantic models 1 Output • A ranked set of semantic models for S
Learn Semantic Types • Learn Semantic Types for each attribute from its data • Pick top K semantic types according to their confidence values 37 dia(title,credit, classification,name,imageURL) title <aac:CulturalHeritageObject, dcterms:title> 0.49 <aac:CulturalHeritageObject, rdfs:label> 0.28 credit <aac:CulturalHeritageObject, dcterms:provenance> 0.83 <aac:Person, ElementsGr2:note> 0.06 classification <skos:Concept, skos:prefLabel> 0.58 <skos:Concept, rdfs:label> 0.41 name <aac:Person, foaf:name> 0.65 <fofa:Person, fofaf:name> 0.32 imageURL <foaf:Document, uri> 0.47 <edm:WebResource, uri> 0.40
Approach 38 Input Learn semantic types for attributes(s) • Sample data from new source (S) • Domain Ontologies (O) • Known semantic models Construct Graph G=(V,E) Generate mappings between attributes(S) and V Generate and rank semantic models 2 Output • A ranked set of semantic models for S
39 • Annotate (tag) nodes and links with list of supporting models • Adjust weight based on the number of supporting models Build Graph G: Add Known Models aac:Person CulturalHeritageObject name creator name hasTypecreated title prefLabel type creationDate title Concept 1 1 1 dm a dm a 1 dm a dm a 1 dm a 1 dm a dma
40 • Annotate (tag) nodes and links with list of supporting models • Adjust weight based on the number of tags Build Graph G: Add Known Models dma npg aac:Person CulturalHeritageObject name creator name hasTypecreated title prefLabel type creationDate title Concept aac:Person name sitter name EuropeanaAggregation WebResource imag e uri aggregatedCHO hasView 0.5 1 1 1 dm a dm a 1 dm a npg 1 npg 1 npg 1 npg 1 dm a npg 0.5 dm a npg 0.5 dm a npg npg
41 Build Graph G: Add Semantic Types title <CulturalHeritageObject,title> <CulturalHeritageObject,label> credit <CulturalHeritageObject,provenance> <Person,note> classification <Concept,prefLabel> <Concept,label> name <aac:Person,name> <foaf:Person,name> imageURL <Document,uri> <WebResource,uri> aac:Person CulturalHeritageObject name creator name hasTypecreated title prefLabel type creationDate title Concept aac:Person name sitter name EuropeanaAggregation WebResource imag e uri aggregatedCHO hasView 0.5 1 1 1 dm a dm a 1 dm a npg 1 npg 1 npg 1 npg 1 dm a npg 0.5 dm a npg 0.5 dm a npg npg
42 Build Graph G: Add Semantic Types title <CulturalHeritageObject,title> <CulturalHeritageObject,label> credit <CulturalHeritageObject,provenance> <Person,note> classification <Concept,prefLabel> <Concept,label> name <aac:Person,name> <foaf:Person,name> imageURL <Document,uri> <WebResource,uri> aac:Person CulturalHeritageObject name creator name hasTypecreated title prefLabel type creationDate title Concept aac:Person name sitter name EuropeanaAggregation WebResource imag e uri aggregatedCHO hasView titl e label 0.5 1 1 1 dm a dm a 1 dm a npg 1 npg 1 npg 1 npg 1 dm a npg 0.5 dm a npg 0.5 dm a npg npg
43 Build Graph G: Add Semantic Types title <CulturalHeritageObject,title> <CulturalHeritageObject,label> credit <CulturalHeritageObject,provenance> <Person,note> classification <Concept,prefLabel> <Concept,label> name <aac:Person,name> <foaf:Person,name> imageURL <Document,uri> <WebResource,uri> aac:Person CulturalHeritageObject name creator name hasTypecreated title prefLabel type creationDate title Concept aac:Person name sitter name note credit foaf:Person EuropeanaAggregation WebResource imag e uri aggregatedCHO hasView Document imageURL name nameclassification note credit label credit titl e provenance label uri 0.5 1 1 1 dm a dm a 1 dm a npg 1 npg 1 npg 1 npg 1 dm a npg 0.5 dm a npg 0.5 dm a npg npg
44 Build Graph G: Expand with Paths from Ontology • Assign a high weight to the links coming from the ontology aac:Person CulturalHeritageObject name creator name hasTypecreated title prefLabel type creationDate title Concept aac:Person name sitter name note credit foaf:Person EuropeanaAggregation WebResource imag e uri aggregatedCHO hasView imageURL name nameclassification note credit label creator Aggregation aggregates subClassOf page credit titl e provenance label uri aggregates isShownAt Document 1000 1000 1000 1000 1000 1000 0.5 1 1 1 dm a dm a 1 dm a npg 1 npg 1 npg 1 npg 1 dm a npg 0.5 dm a npg 0.5 dm a npg npg
Approach 45 Input Learn semantic types for attributes(s) • Sample data from new source (S) • Domain Ontologies (O) • Known semantic models Construct Graph G=(V,E) Generate mappings between attributes(S) and V Generate and rank semantic models 3 Output • A ranked set of semantic models for S
46 Map Source Attributes to the Graph title <CulturalHeritageObject,title> <CulturalHeritageObject,label> credit <CulturalHeritageObject,provenance> <Person,note> classification <Concept,prefLabel> <Concept,label> name <aac:Person,name> <foaf:Person,name> imageURL <Document,uri> <WebResource,uri> aac:Person CulturalHeritageObject name creator name hasTypecreated title prefLabel type creationDate title Concept aac:Person name sitter name note credit foaf:Person EuropeanaAggregation WebResource imag e uri aggregatedCHO hasView Document imageURL name nameclassification note credit label creator Aggregation aggregates subClassOf page credit titl e provenance label uri aggregates isShownAt1000 1000 1000 1000 1000 1000 0.5 1 1 1 dm a dm a 1 dm a npg 1 npg 1 npg 1 npg 1 dm a npg 0.5 dm a npg 0.5 dm a npg npg
47 Map Source Attributes to the Graph title <CulturalHeritageObject,title> <CulturalHeritageObject,label> credit <CulturalHeritageObject,provenance> <Person,note> classification <Concept,prefLabel> <Concept,label> name <aac:Person,name> <foaf:Person,name> imageURL <Document,uri> <WebResource,uri> aac:Person CulturalHeritageObject name creator name hasTypecreated title prefLabel type creationDate title Concept aac:Person name sitter name note credit foaf:Person EuropeanaAggregation WebResource imag e uri aggregatedCHO hasView Document imageURL name nameclassification note credit label creator Aggregation aggregates subClassOf page credit titl e provenance label uri aggregates isShownAt1000 1000 1000 1000 1000 1000 0.5 1 1 1 dm a dm a 1 dm a npg 1 npg 1 npg 1 npg 1 dm a npg 0.5 dm a npg 0.5 dm a npg npg
48 Map Source Attributes to the Graph title <CulturalHeritageObject,title> <CulturalHeritageObject,label> credit <CulturalHeritageObject,provenance> <Person,note> classification <Concept,prefLabel> <Concept,label> name <aac:Person,name> <foaf:Person,name> imageURL <Document,uri> <WebResource,uri> aac:Person CulturalHeritageObject name creator name hasTypecreated prefLabel type creationDate title Concept aac:Person name sitter name note credit foaf:Person EuropeanaAggregation WebResource imag e uri aggregatedCHO hasView Document imageURL name nameclassification note credit label creator Aggregation aggregates subClassOf page credit titl e provenance label uri aggregates isShownAt title 1000 1000 1000 1000 1000 1000 0.5 1 1 1 dm a dm a 1 dm a npg 1 npg 1 npg 1 npg 1 dm a npg 0.5 dm a npg 0.5 dm a npg npg
Approach 51 Input Learn semantic types for attributes(s) • Sample data from new source (S) • Domain Ontologies (O) • Known semantic models Construct Graph G=(V,E) Generate mappings between attributes(S) and V Generate and rank semantic models4 Output • A ranked set of semantic models for S
Generate Semantic Models • Compute Steiner tree for each mapping – A minimal tree connecting nodes of mapping – A customization of BANKS algorithm [Bhalotia et al., 2002] • Our algorithm considers both coherence and popularity • Each tree is a candidate model • Rank the models based on coherence and cost 52
What Is Coherence? 53 PlacePerson organizer Event location s1 s2 s3 Person bornIn Place Person bornIn Place Known Models
What Is Coherence? 54 PlacePerson organizer Event location s1 s2 s3 Person bornIn Place Person bornIn Place PlacePerson organizer Event location Graph 1 1 bornIn0. 5 s2, s3 s1s1 Known Models
What Is Coherence? 55 PlacePerson organizer Event location s1 s2 s3 Person bornIn Place Person bornIn Place PlacePerson organizer Event location Graph 1 1 bornIn0. 5 s2, s3 s1s1 Known Models Semantic types of a new source Person Event Place
What Is Coherence? 56 PlacePerson organizer Event location s1 s2 s3 Person bornIn Place Person bornIn Place PlacePerson organizer Event location 1 1 bornIn0. 5 s2, s3 s1s1 Top 3 Steiner trees Known Models PlacePerson organizer Event 1 bornIn0. 5 s2, s3 s1 PlacePerson Event location 1 bornIn0. 5 s2, s3 s1 PlacePerson organizer Event location 1 1 s1s1 Person Event Place Semantic types of a new source Not minimal model but more coherent Graph
57 Example Mapping title <CulturalHeritageObject,title> <CulturalHeritageObject,label> credit <CulturalHeritageObject,provenance> <Person,note> classification <Concept,prefLabel> <Concept,label> name <aac:Person,name> <foaf:Person,name> imageURL <Document,uri> <WebResource,uri> aac:Person CulturalHeritageObject name creator name hasTypecreated title prefLabel type creationDate title Concept aac:Person name sitter name note credit foaf:Person EuropeanaAggregation WebResource imag e uri hasView Document imageURL name nameclassification note credit label creator Aggregation aggregates subClassOf page credit titl e provenance label uri isShownAt1000 1000 1000 1000 1000 1000 0.5 1 1 1 dm a dm a 1 dm a npg 1 npg 1 npg 1 npg 1 dm a npg 0.5 dm a npg 0.5 dm a npg npg aggregatedCHO aggregates
58 Steiner Tree title <CulturalHeritageObject,title> <CulturalHeritageObject,label> credit <CulturalHeritageObject,provenance> <Person,note> classification <Concept,prefLabel> <Concept,label> name <aac:Person,name> <foaf:Person,name> imageURL <Document,uri> <WebResource,uri> aac:Person CulturalHeritageObject name creator name hasTypecreated title prefLabel type creationDate title Concept aac:Person name sitter name note credit foaf:Person EuropeanaAggregation WebResource imag e uri hasView Document imageURL name nameclassification note credit label creator Aggregation aggregates subClassOf page credit titl e provenance label uri isShownAt1000 1000 1000 1000 1000 1000 0.5 1 1 1 dm a dm a 1 dm a npg 1 npg 1 npg 1 npg 1 dm a npg 0.5 dm a npg 0.5 dm a npg npg aggregatedCHO aggregates
Final Model in Karma 59 EDM SKOS FOAF AAC ElementsGr2ORE DCTermsDomain ontologies: Domain: Museum Data Source: Detroit Institute of Art  dia(title,credit,classification,name,imageURL)
Evaluation 60 Evaluation Dataset EDM CRM # sources 29 29 # classes in the ontologies 119 147 # properties in the ontologies 351 409 # nodes in the gold standard models 473 812 # links in the gold standard models 444 785
CRM Gold Standard Models-Example 61
62 CRM Gold Standard Models-Example
User Effort 63 source columns Choose Type Change Link Time (min) s1 7 7 1 3 s2 12 5 2 => 1 6 s3 4 0 0 2 s4 17 5 7 => 6 8 s5 14 4 6 => 2 7 s6 18 4 4 => 1 7 s7 14 1 4 => 0 6 s8 6 0 4 => 0 3 … … … … … s29 9 2 1 3 Total 329 56 96 => 19 128 => 101 Avg. min per source: 4.4 3.4 minutes Avg. # user actions per source: 5.2 2.6
Accuracy Compute precision and recall between learned models and correct models 64 precision = rel(sm)Çrel(sm') rel(sm') recall = rel(sm)Çrel(sm') rel(sm) How many of the learned relationships are correct? How many of the correct relationships are learned? Person Artwork location Museum creator correctmodel Person Museum location Artwork founder learnedmodel <Artwork,location,Museum> <Artwork,creator,Person> <Museum,founder,Person> <Artwork,location,Museum> Precision: 0.5, Recall: 0.5
Experiment 1 correct semantic types are given 65 0.0 0.2 0.4 0.6 0.8 1.0 0 4 8 12 16 20 24 28 Number of known semantic models precision recall 0.0 0.2 0.4 0.6 0.8 1.0 0 4 8 12 16 20 24 28 Number of known semantic models precision recall
Experiment 2 learn semantic types, pick top K candidates 68 0.0 0.2 0.4 0.6 0.8 0 4 8 12 16 20 24 28 Number of known semantic models precision (k=1) recall (k=1) precision (k=4) recall (k=4) 0.0 0.2 0.4 0.6 0.8 0 4 8 12 16 20 24 28 Number of known semantic models precision (k=1) recall (k=1) precision (k=4) recall (k=4)
Limitation • Lack of sufficient known semantic models is some domains 70
Inferring Semantic Relations from Linked Open Data Contribution: leveraging graph patterns in LOD to infer relationships
Idea • There is a huge amount of linked data available in many domains (RDF format) 72 • Use LOD when there is no known semantic model • Exploit the relationships between instances
Approach [Taheriyan et al, COLD 2015] Domain Ontology Learn Semantic Types 73 Sample Data Construct a Graph Generate Candidate Models Rank Results Linked Open Data Extract Patterns
LOD Patterns 74 ../person- institution/57551 E21_Person rdf:type Thomas Burgon skos:prefLabel ../person- institution/57551/birthP98i_was_born ../person- institution/57551/birth/ date P4_has_time-span E67_Birth rdf:type 1787 rdfs:label E52_Time-Span rdf:type LOD Fragment from the British Museum
LOD Patterns 75 E67_BirthE21_Person P98i_was_born ../person- institution/57551 E21_Person rdf:type Thomas Burgon skos:prefLabel ../person- institution/57551/birthP98i_was_born ../person- institution/57551/birth/ date P4_has_time-span E67_Birth rdf:type 1787 rdfs:label E52_Time-Span P4_has_time-span E52_Time-Span rdf:type LOD Fragment from the British Museum Pattern
Pattern Templates • Many possible templates for patterns – Example: patterns for classes C1, C2, C3 • Consider only tree patterns • Limit the length of the patterns 76
Evaluation • Linked data: 3,398,350 triples published by Smithsonian American Art Museum • Correct semantic types given • Extracted patterns of length 1 and 2 78 Evaluation Dataset CRM # sources 29 # classes in the ontologies 147 # properties in the ontologies 409 # nodes in the gold standard models 812 # links in the gold standard models 785 background knowledge precision recall time (s) domain ontology 0.07 0.05 0.17 domain ontology + patterns of length 1 0.65 0.55 0.75 domain ontology + patterns of length 1 and 2 0.78 0.70 0.46
Related Work
Related Work • Mapping databases and spreadsheets to ontologies – Mapping languages and tools (D2R, R2RML) – String similarity between column names and ontology terms • Understand semantics of Web tables – Use column headers and cell values to find the labels and relations from a database of labels and relations populated from the Web • Exploit Linked Open Data (LOD) – Link the values to the entities in LOD to find the types of the values and their relationships • Learn semantic definitions of online information sources – Learns logical rules from known sources – Only learns descriptions that are conjunctive combinations of known descriptions 80
Discussion & Future Work
Discussion • Contributions – Semi-automatically model the relationships – Learn semantic models from previous models – Infer semantic relationships from LOD • Provide explicit semantics for large portion of LOD • Help to publish consistent RDF data • Applications – VIVO – Smithsonian American Art Museum – DIG for DARPA’s Memex project 82
Future Work • Improve the quality of semantic labeling – Use LOD to learn semantic types • Extract longer patterns from LOD • Publish linked data – Transform the data to a common vocabulary – Linking entities across different datasets 83

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Learning the Semantics of Structured Data Sources

  • 1.
    Learning the Semanticsof Structured Data Sources Mohsen Taheriyan
  • 2.
    Motivation 2 How to expressthe intended meaning of data? Explicit semantics is missing in many of the structured sources name date city state workplace 1 Fred Collins Oct 1959 Seattle WA Microsoft 2 Tina Peterson May 1980 New York NY Google Employee? CEO? Birth date? Death date? Employment date? Person? Organization? Birth city? Work city?
  • 3.
    Semantic Model Map thesource to the classes & properties in an ontology object property data property subClassOf Person Organization Place Stat e name birthdate bornIn worksFor state name phone name livesIn City Event ceo location organizer nearby startDate title isPartOf postalCode 3 name date city state workplace 1 Fred Collins Oct 1959 Seattle WA Microsoft 2 Tina Peterson May 1980 New York NY Google SourceDomainOntology
  • 4.
    Semantic Types Person OrganizationCityState name birthdate name namename 4 Person name date city state workplace 1 Fred Collins Oct 1959 Seattle WA Microsoft 2 Tina Peterson May 1980 New York NY Google
  • 5.
    Relationships OrganizationCity State name birthdatename namename 5 Person name date city state workplace 1 Fred Collins Oct 1959 Seattle WA Microsoft 2 Tina Peterson May 1980 New York NY Google bornIn worksFor state
  • 6.
    Problem: How to automatebuilding semantic models for structured sources?
  • 7.
    Outline • Semi-automatically buildingsemantic models • Learning semantics models from known models • Inferring semantic relations from LOD • Related Work • Discussion & Future Work 8
  • 8.
    Semi-automatically Building Semantic Models Contribution:a graph-based approach to extract implicit relationships
  • 9.
    Approach [Knoblock et al,ESWC 2012] 10 Domain Ontology Learn Semantic Types Extract Relationships Steiner Tree Sample Data Construct a Graph Implemented in Karma http://www.isi.edu/integration/karma @KarmaSemWe b
  • 10.
    Example Source object property data property subClassOf DomainOntology 12 name date city state workplace 1 Fred Collins Oct 1959 Seattle WA Microsoft 2 Tina Peterson May 1980 New York NY Google Goal: Find a semantic model for the source (map the source to the ontology)
  • 11.
    Learning Semantic Types [Krishnamurthyet al., ESWC 2015] 13 class? property ? workplace Google Microsoft Amazon …
  • 12.
  • 13.
  • 14.
  • 15.
    Semantic Labeling Approach •Each semantic type: label • Each data column: document • Textual Data – Compute TF/IDF vectors for documents – Compare documents using Cosine Similarity between TF/IDF vectors • Numeric Data – Use Statistical Hypothesis Testing – Intuition: distribution of values in different semantic types is different, e.g., temperature vs. population • Return Top-k suggestions based on the confidence scores 17
  • 16.
    Construct a Graph Constructa graph from semantic types and ontology 18 Person OrganizationCity State name birthdate name namename Person name date city state workplace 1 Fred Collins Oct 1959 Seattle WA Microsoft 2 Tina Peterson May 1980 New York NY Google
  • 17.
    Construct a Graph Constructa graph from semantic types and ontology date 19
  • 18.
    Inferring the Relationships Selectminimal tree that connects all semantic types – A customized Steiner tree algorithm 22 date
  • 19.
  • 20.
    Refining the Model 24 Imposeconstraints on Steiner Tree Algorithm – Change weight of selected links to ε – Add source and target of selected link to Steiner nodes date
  • 21.
  • 22.
    Evaluation 26 Evaluation Dataset EDM #sources 29 # classes in the ontologies 119 # properties in the ontologies 351 # nodes in the gold standard models 473 # links in the gold standard models 444 • Measured the user effort in Karma to model the sources • Started with no training data • User actions – Assign/Change semantic types – Change relationships
  • 23.
    User Effort 27 source columnsChoose Type Change Link Time (min) s1 7 7 1 3 s2 12 5 2 6 s3 4 0 0 2 s4 17 5 7 8 s5 14 4 6 7 s6 18 4 4 7 s7 14 1 4 6 s8 6 0 4 3 … … … … … s29 9 2 1 3 Total 329 56 96 128 Avg. min per source: 4.4 minutes Avg. # user actions per source: 152/29=5.2
  • 24.
    Limitation • This approachdoes not learn the changes done by the user in relationships • User has to go through the refinement process each time 28
  • 25.
    Learning Semantic Models Contribution:exploiting known semantic models to learn relationships
  • 26.
    Main Idea 30 Sources inthe same domain often have similar data Exploit knowledge of known semantic models to hypothesize a semantic model for a new sources
  • 27.
    Example 31 EDM SKOS FOAFAAC ElementsGr2ORE DCTermsDomain ontologies: Source: Dallas Museum of Art  dma(title,creationDate,name,type) Domain: Museum Data
  • 28.
    Example 32 EDM SKOS FOAFAAC ElementsGr2ORE DCTermsDomain ontologies: Domain: Museum Data Source: National Portrait Gallery  npg(name,artist,year,image)
  • 29.
    Example 33 EDM SKOS FOAFAAC ElementsGr2ORE DCTermsDomain ontologies: Domain: Museum Data Goal: Automatically suggest a semantic model for dia Source: Detroit Institute of Art  dia(title,credit,classification,name,imageURL)
  • 30.
    Approach [Taheriyan et al,ISWC 2013, ICSC 2014, JWS 2015] Domain Ontology Learn Semantic Types 34 Sample Data Construct a Graph Generate Candidate Models Rank Results Known Semantic Models Implemented in Karma
  • 31.
    Approach 36 Input Learn semantic typesfor attributes(s) • Sample data from new source (S) • Domain Ontologies (O) • Known semantic models Construct Graph G=(V,E) Generate mappings between attributes(S) and V Generate and rank semantic models 1 Output • A ranked set of semantic models for S
  • 32.
    Learn Semantic Types •Learn Semantic Types for each attribute from its data • Pick top K semantic types according to their confidence values 37 dia(title,credit, classification,name,imageURL) title <aac:CulturalHeritageObject, dcterms:title> 0.49 <aac:CulturalHeritageObject, rdfs:label> 0.28 credit <aac:CulturalHeritageObject, dcterms:provenance> 0.83 <aac:Person, ElementsGr2:note> 0.06 classification <skos:Concept, skos:prefLabel> 0.58 <skos:Concept, rdfs:label> 0.41 name <aac:Person, foaf:name> 0.65 <fofa:Person, fofaf:name> 0.32 imageURL <foaf:Document, uri> 0.47 <edm:WebResource, uri> 0.40
  • 33.
    Approach 38 Input Learn semantic typesfor attributes(s) • Sample data from new source (S) • Domain Ontologies (O) • Known semantic models Construct Graph G=(V,E) Generate mappings between attributes(S) and V Generate and rank semantic models 2 Output • A ranked set of semantic models for S
  • 34.
    39 • Annotate (tag)nodes and links with list of supporting models • Adjust weight based on the number of supporting models Build Graph G: Add Known Models aac:Person CulturalHeritageObject name creator name hasTypecreated title prefLabel type creationDate title Concept 1 1 1 dm a dm a 1 dm a dm a 1 dm a 1 dm a dma
  • 35.
    40 • Annotate (tag)nodes and links with list of supporting models • Adjust weight based on the number of tags Build Graph G: Add Known Models dma npg aac:Person CulturalHeritageObject name creator name hasTypecreated title prefLabel type creationDate title Concept aac:Person name sitter name EuropeanaAggregation WebResource imag e uri aggregatedCHO hasView 0.5 1 1 1 dm a dm a 1 dm a npg 1 npg 1 npg 1 npg 1 dm a npg 0.5 dm a npg 0.5 dm a npg npg
  • 36.
    41 Build Graph G:Add Semantic Types title <CulturalHeritageObject,title> <CulturalHeritageObject,label> credit <CulturalHeritageObject,provenance> <Person,note> classification <Concept,prefLabel> <Concept,label> name <aac:Person,name> <foaf:Person,name> imageURL <Document,uri> <WebResource,uri> aac:Person CulturalHeritageObject name creator name hasTypecreated title prefLabel type creationDate title Concept aac:Person name sitter name EuropeanaAggregation WebResource imag e uri aggregatedCHO hasView 0.5 1 1 1 dm a dm a 1 dm a npg 1 npg 1 npg 1 npg 1 dm a npg 0.5 dm a npg 0.5 dm a npg npg
  • 37.
    42 Build Graph G:Add Semantic Types title <CulturalHeritageObject,title> <CulturalHeritageObject,label> credit <CulturalHeritageObject,provenance> <Person,note> classification <Concept,prefLabel> <Concept,label> name <aac:Person,name> <foaf:Person,name> imageURL <Document,uri> <WebResource,uri> aac:Person CulturalHeritageObject name creator name hasTypecreated title prefLabel type creationDate title Concept aac:Person name sitter name EuropeanaAggregation WebResource imag e uri aggregatedCHO hasView titl e label 0.5 1 1 1 dm a dm a 1 dm a npg 1 npg 1 npg 1 npg 1 dm a npg 0.5 dm a npg 0.5 dm a npg npg
  • 38.
    43 Build Graph G:Add Semantic Types title <CulturalHeritageObject,title> <CulturalHeritageObject,label> credit <CulturalHeritageObject,provenance> <Person,note> classification <Concept,prefLabel> <Concept,label> name <aac:Person,name> <foaf:Person,name> imageURL <Document,uri> <WebResource,uri> aac:Person CulturalHeritageObject name creator name hasTypecreated title prefLabel type creationDate title Concept aac:Person name sitter name note credit foaf:Person EuropeanaAggregation WebResource imag e uri aggregatedCHO hasView Document imageURL name nameclassification note credit label credit titl e provenance label uri 0.5 1 1 1 dm a dm a 1 dm a npg 1 npg 1 npg 1 npg 1 dm a npg 0.5 dm a npg 0.5 dm a npg npg
  • 39.
    44 Build Graph G:Expand with Paths from Ontology • Assign a high weight to the links coming from the ontology aac:Person CulturalHeritageObject name creator name hasTypecreated title prefLabel type creationDate title Concept aac:Person name sitter name note credit foaf:Person EuropeanaAggregation WebResource imag e uri aggregatedCHO hasView imageURL name nameclassification note credit label creator Aggregation aggregates subClassOf page credit titl e provenance label uri aggregates isShownAt Document 1000 1000 1000 1000 1000 1000 0.5 1 1 1 dm a dm a 1 dm a npg 1 npg 1 npg 1 npg 1 dm a npg 0.5 dm a npg 0.5 dm a npg npg
  • 40.
    Approach 45 Input Learn semantic typesfor attributes(s) • Sample data from new source (S) • Domain Ontologies (O) • Known semantic models Construct Graph G=(V,E) Generate mappings between attributes(S) and V Generate and rank semantic models 3 Output • A ranked set of semantic models for S
  • 41.
    46 Map Source Attributesto the Graph title <CulturalHeritageObject,title> <CulturalHeritageObject,label> credit <CulturalHeritageObject,provenance> <Person,note> classification <Concept,prefLabel> <Concept,label> name <aac:Person,name> <foaf:Person,name> imageURL <Document,uri> <WebResource,uri> aac:Person CulturalHeritageObject name creator name hasTypecreated title prefLabel type creationDate title Concept aac:Person name sitter name note credit foaf:Person EuropeanaAggregation WebResource imag e uri aggregatedCHO hasView Document imageURL name nameclassification note credit label creator Aggregation aggregates subClassOf page credit titl e provenance label uri aggregates isShownAt1000 1000 1000 1000 1000 1000 0.5 1 1 1 dm a dm a 1 dm a npg 1 npg 1 npg 1 npg 1 dm a npg 0.5 dm a npg 0.5 dm a npg npg
  • 42.
    47 Map Source Attributesto the Graph title <CulturalHeritageObject,title> <CulturalHeritageObject,label> credit <CulturalHeritageObject,provenance> <Person,note> classification <Concept,prefLabel> <Concept,label> name <aac:Person,name> <foaf:Person,name> imageURL <Document,uri> <WebResource,uri> aac:Person CulturalHeritageObject name creator name hasTypecreated title prefLabel type creationDate title Concept aac:Person name sitter name note credit foaf:Person EuropeanaAggregation WebResource imag e uri aggregatedCHO hasView Document imageURL name nameclassification note credit label creator Aggregation aggregates subClassOf page credit titl e provenance label uri aggregates isShownAt1000 1000 1000 1000 1000 1000 0.5 1 1 1 dm a dm a 1 dm a npg 1 npg 1 npg 1 npg 1 dm a npg 0.5 dm a npg 0.5 dm a npg npg
  • 43.
    48 Map Source Attributesto the Graph title <CulturalHeritageObject,title> <CulturalHeritageObject,label> credit <CulturalHeritageObject,provenance> <Person,note> classification <Concept,prefLabel> <Concept,label> name <aac:Person,name> <foaf:Person,name> imageURL <Document,uri> <WebResource,uri> aac:Person CulturalHeritageObject name creator name hasTypecreated prefLabel type creationDate title Concept aac:Person name sitter name note credit foaf:Person EuropeanaAggregation WebResource imag e uri aggregatedCHO hasView Document imageURL name nameclassification note credit label creator Aggregation aggregates subClassOf page credit titl e provenance label uri aggregates isShownAt title 1000 1000 1000 1000 1000 1000 0.5 1 1 1 dm a dm a 1 dm a npg 1 npg 1 npg 1 npg 1 dm a npg 0.5 dm a npg 0.5 dm a npg npg
  • 44.
    Approach 51 Input Learn semantic typesfor attributes(s) • Sample data from new source (S) • Domain Ontologies (O) • Known semantic models Construct Graph G=(V,E) Generate mappings between attributes(S) and V Generate and rank semantic models4 Output • A ranked set of semantic models for S
  • 45.
    Generate Semantic Models •Compute Steiner tree for each mapping – A minimal tree connecting nodes of mapping – A customization of BANKS algorithm [Bhalotia et al., 2002] • Our algorithm considers both coherence and popularity • Each tree is a candidate model • Rank the models based on coherence and cost 52
  • 46.
    What Is Coherence? 53 PlacePerson organizer Event location s1s2 s3 Person bornIn Place Person bornIn Place Known Models
  • 47.
    What Is Coherence? 54 PlacePerson organizer Event location s1s2 s3 Person bornIn Place Person bornIn Place PlacePerson organizer Event location Graph 1 1 bornIn0. 5 s2, s3 s1s1 Known Models
  • 48.
    What Is Coherence? 55 PlacePerson organizer Event location s1s2 s3 Person bornIn Place Person bornIn Place PlacePerson organizer Event location Graph 1 1 bornIn0. 5 s2, s3 s1s1 Known Models Semantic types of a new source Person Event Place
  • 49.
    What Is Coherence? 56 PlacePerson organizer Event location s1s2 s3 Person bornIn Place Person bornIn Place PlacePerson organizer Event location 1 1 bornIn0. 5 s2, s3 s1s1 Top 3 Steiner trees Known Models PlacePerson organizer Event 1 bornIn0. 5 s2, s3 s1 PlacePerson Event location 1 bornIn0. 5 s2, s3 s1 PlacePerson organizer Event location 1 1 s1s1 Person Event Place Semantic types of a new source Not minimal model but more coherent Graph
  • 50.
    57 Example Mapping title <CulturalHeritageObject,title><CulturalHeritageObject,label> credit <CulturalHeritageObject,provenance> <Person,note> classification <Concept,prefLabel> <Concept,label> name <aac:Person,name> <foaf:Person,name> imageURL <Document,uri> <WebResource,uri> aac:Person CulturalHeritageObject name creator name hasTypecreated title prefLabel type creationDate title Concept aac:Person name sitter name note credit foaf:Person EuropeanaAggregation WebResource imag e uri hasView Document imageURL name nameclassification note credit label creator Aggregation aggregates subClassOf page credit titl e provenance label uri isShownAt1000 1000 1000 1000 1000 1000 0.5 1 1 1 dm a dm a 1 dm a npg 1 npg 1 npg 1 npg 1 dm a npg 0.5 dm a npg 0.5 dm a npg npg aggregatedCHO aggregates
  • 51.
    58 Steiner Tree title <CulturalHeritageObject,title><CulturalHeritageObject,label> credit <CulturalHeritageObject,provenance> <Person,note> classification <Concept,prefLabel> <Concept,label> name <aac:Person,name> <foaf:Person,name> imageURL <Document,uri> <WebResource,uri> aac:Person CulturalHeritageObject name creator name hasTypecreated title prefLabel type creationDate title Concept aac:Person name sitter name note credit foaf:Person EuropeanaAggregation WebResource imag e uri hasView Document imageURL name nameclassification note credit label creator Aggregation aggregates subClassOf page credit titl e provenance label uri isShownAt1000 1000 1000 1000 1000 1000 0.5 1 1 1 dm a dm a 1 dm a npg 1 npg 1 npg 1 npg 1 dm a npg 0.5 dm a npg 0.5 dm a npg npg aggregatedCHO aggregates
  • 52.
    Final Model inKarma 59 EDM SKOS FOAF AAC ElementsGr2ORE DCTermsDomain ontologies: Domain: Museum Data Source: Detroit Institute of Art  dia(title,credit,classification,name,imageURL)
  • 53.
    Evaluation 60 Evaluation Dataset EDMCRM # sources 29 29 # classes in the ontologies 119 147 # properties in the ontologies 351 409 # nodes in the gold standard models 473 812 # links in the gold standard models 444 785
  • 54.
    CRM Gold StandardModels-Example 61
  • 55.
    62 CRM Gold StandardModels-Example
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    User Effort 63 source columnsChoose Type Change Link Time (min) s1 7 7 1 3 s2 12 5 2 => 1 6 s3 4 0 0 2 s4 17 5 7 => 6 8 s5 14 4 6 => 2 7 s6 18 4 4 => 1 7 s7 14 1 4 => 0 6 s8 6 0 4 => 0 3 … … … … … s29 9 2 1 3 Total 329 56 96 => 19 128 => 101 Avg. min per source: 4.4 3.4 minutes Avg. # user actions per source: 5.2 2.6
  • 57.
    Accuracy Compute precision andrecall between learned models and correct models 64 precision = rel(sm)Çrel(sm') rel(sm') recall = rel(sm)Çrel(sm') rel(sm) How many of the learned relationships are correct? How many of the correct relationships are learned? Person Artwork location Museum creator correctmodel Person Museum location Artwork founder learnedmodel <Artwork,location,Museum> <Artwork,creator,Person> <Museum,founder,Person> <Artwork,location,Museum> Precision: 0.5, Recall: 0.5
  • 58.
    Experiment 1 correct semantictypes are given 65 0.0 0.2 0.4 0.6 0.8 1.0 0 4 8 12 16 20 24 28 Number of known semantic models precision recall 0.0 0.2 0.4 0.6 0.8 1.0 0 4 8 12 16 20 24 28 Number of known semantic models precision recall
  • 59.
    Experiment 2 learn semantictypes, pick top K candidates 68 0.0 0.2 0.4 0.6 0.8 0 4 8 12 16 20 24 28 Number of known semantic models precision (k=1) recall (k=1) precision (k=4) recall (k=4) 0.0 0.2 0.4 0.6 0.8 0 4 8 12 16 20 24 28 Number of known semantic models precision (k=1) recall (k=1) precision (k=4) recall (k=4)
  • 60.
    Limitation • Lack ofsufficient known semantic models is some domains 70
  • 61.
    Inferring Semantic Relations fromLinked Open Data Contribution: leveraging graph patterns in LOD to infer relationships
  • 62.
    Idea • There isa huge amount of linked data available in many domains (RDF format) 72 • Use LOD when there is no known semantic model • Exploit the relationships between instances
  • 63.
    Approach [Taheriyan et al,COLD 2015] Domain Ontology Learn Semantic Types 73 Sample Data Construct a Graph Generate Candidate Models Rank Results Linked Open Data Extract Patterns
  • 64.
  • 65.
  • 66.
    Pattern Templates • Manypossible templates for patterns – Example: patterns for classes C1, C2, C3 • Consider only tree patterns • Limit the length of the patterns 76
  • 67.
    Evaluation • Linked data:3,398,350 triples published by Smithsonian American Art Museum • Correct semantic types given • Extracted patterns of length 1 and 2 78 Evaluation Dataset CRM # sources 29 # classes in the ontologies 147 # properties in the ontologies 409 # nodes in the gold standard models 812 # links in the gold standard models 785 background knowledge precision recall time (s) domain ontology 0.07 0.05 0.17 domain ontology + patterns of length 1 0.65 0.55 0.75 domain ontology + patterns of length 1 and 2 0.78 0.70 0.46
  • 68.
  • 69.
    Related Work • Mappingdatabases and spreadsheets to ontologies – Mapping languages and tools (D2R, R2RML) – String similarity between column names and ontology terms • Understand semantics of Web tables – Use column headers and cell values to find the labels and relations from a database of labels and relations populated from the Web • Exploit Linked Open Data (LOD) – Link the values to the entities in LOD to find the types of the values and their relationships • Learn semantic definitions of online information sources – Learns logical rules from known sources – Only learns descriptions that are conjunctive combinations of known descriptions 80
  • 70.
  • 71.
    Discussion • Contributions – Semi-automaticallymodel the relationships – Learn semantic models from previous models – Infer semantic relationships from LOD • Provide explicit semantics for large portion of LOD • Help to publish consistent RDF data • Applications – VIVO – Smithsonian American Art Museum – DIG for DARPA’s Memex project 82
  • 72.
    Future Work • Improvethe quality of semantic labeling – Use LOD to learn semantic types • Extract longer patterns from LOD • Publish linked data – Transform the data to a common vocabulary – Linking entities across different datasets 83

Editor's Notes

  • #6 Key ingredient to automate: Source discovery, Data integration, Publish knowledge graphs
  • #22 In the second step, instead of selecting MST ((v1, v4) – (v1, v2)- (v2-v3)), if we select another MST like ((v1, v4) – (v1, v2)- (v1-v3)), we would get another Steiner tree as result. MST = Minimum Spanning Tree
  • #23 The exact approximation ratio is: 2 * (1 – 1/l) where l is the number of leaves in optimal tree. Paper link: http://www.springerlink.com/content/v7w86m72174k7267/ Volume 15, Number 2, 141-145, DOI: 10.1007/BF00288961 A fast algorithm for Steiner trees L. Kou, G. Markowsky and L. Berman
  • #28 Out of the 56 manual assignments, 19 were for specifying semantic types that the system had never seen before. 0.46 action per column
  • #31 http://www.metmuseum.org/collection/the-collection-online/search?deptids=1&amp;pg=1&amp;ft=french&amp;od=on&amp;ao=on&amp;noqs=true http://americanart.si.edu/collections/search/artwork/results/index.cfm?rows=10&fq=online_media_type%3A%22Images%22&q=Search+by+Artist%2C+Work%2C+or+Keyword&page=1&start=0&x=62&y=5 http://museum.dma.org:9090/emuseum/view/objects/asitem/2031/0/title-desc?t:state:flow=ff495581-e0d2-4334-bec9-19988f9eeb20 http://www.mfah.org/art/100-highlights/commemorative-head-king/ Leverage relationships in known semantic models to hypothesize relationships for new sources
  • #38 Semantic Type: <class_uri, property_uri> Cosine similarity between TF/IDF vectors (for textual data) and statistical hypothesis testing (for numeric data)
  • #53 Keyword Searching and Browsing in Databases using BANKS
  • #61 ds edm dscrm #data source 29 29 #classes in the domain ontologies 119 147 #properties in the domain ontologies 351 409 #nodes in the gold-standard models 473 812 #data nodes in the gold-standard models 331 418 #class nodes in the gold-standard models 142 394 #links in the gold-standard models 444 785
  • #62 Indiana Museum of Art
  • #63 Dallas Museum of Art
  • #64 Out of the 56 manual assignments, 19 were for specifying semantic types that the system had never seen before. 0.46 action per column
  • #66 edm: 113 links, crm: 367 links
  • #69 edm: recall: 71->77 precidion: 71->79 crm: recall: 62->69 precidion: 65->71
  • #81 Mapping databases and spreadsheets to ontologies Mapping languages: D2R [Bizer, 2003], D2RQ [Bizer and Seaborne, 2004], R2RML [Das et al., 2012] Tools: RDOTE [Vavliakis et al., 2010], RDF123 [Han et al., 2008], XLWrap [Langegger and Woß, 2009] String similarity between column names and ontology terms [Polfliet and Ichise, 2010] Understand semantics of Web tables Use column headers and cell values to find the labels and relations from a database of labels and relations populated from the Web [Wang et al., 2012] [Limaye et al., 2010] [Venetis et al., 2011] Exploit Linked Open Data (LOD) Link the values to the entities in LOD to find the types of the values and their relationships [Muoz et al., 2013] [Mulwad et al., 2013] Semantic annotation of Web services Languages: SAWSDL [Farrell and Lausen, 2007] Tools: SWEET [Maleshkova et al., 2009] Annotate input and output parameters [Heß et al., 2003] [Lerman et al., 2006] [Saquicela e al., 2011] Learn semantic definitions of online information sources [Carman, Knoblock, 2007] Learns LAV rules from known sources Only learns descriptions that are conjunctive combinations of known descriptions Learn semantic models of structured data sources [Taheriyan et al, 2013, 2014, 2015] Learns complete semantic models from previously modeled sources
  • #83 A possible direction for future work is to perform user evaluations to measure the quality of the models produced using learning algorithms. It is much harder for users to model a source from scratch A large portion of the data in the LOD cloud is published directly from existing databases using tools such as D2R. This conversion process uses the structure of the data as it is organized in the database. There is often no explicit semantic description of the contents of a source and it requires a significant effort if one wants to do more than simply convert a database into RDF - Often, there are multiple correct ways to model the same type of data. For example, users can use Dublin Core and FOAF to model the creator relationship between a person and an object (dcterms:creator and foaf:maker). A community is better served when all the data with the same semantics is modeled using the same classes and properties. Our work encourages consistency because our learning algorithms bias the selection of classes and properties towards those used more frequently in existing models.
  • #87 linked to DBpedia, the Getty Union List of Artist Names (ULAN)® and the NY Times Linked Data
  • #88 linked to DBpedia, the Getty Union List of Artist Names (ULAN)® and the NY Times Linked Data
  • #89 An et al. [An et al., 2007] generate declarative mapping expressions between two tables with different schemas starting from element correspondences. They create a graph from the conceptual model (CM) of each schema and then suggest plausible mappings by exploring low-cost Steiner trees that connect those nodes in the CM graph that have attributes participating in element correspondences. Known: Table 1, CM graph 1, marked nodes (nodes in CM1 corresponding to columns), s-tree1: a semantic tree that expresses the correct semantic of Table1 by connecting its marked nodes in CM1 Known: Table 2, CM graph 2, marked nodes (nodes in CM2 corresponding to columns), s-tree2: a semantic tree that expresses the correct semantic of Table2 by connecting its marked nodes in CM2 Goal: Find a mapping from Table1 to Table2 (a subgraph of CM1, called CSG1, to a subgraph of CM2, called CSG2 Method: If CSG2 is known (e.g., it is the s-tree2), find the Steiner tree in CM1 connecting marked nodes, preferring the edges from s-tree1 Strong assumption: we know semantic of each table (s-trees) Use-case example: Table 1 has 10 columns with a large s-tree, and table 2 has only 3 columns. This approach finds a minimal tree in CM1 (maximum overlap with s-tree1) that connects the marked nodes of table1 corresponding to the marked nodes of table2.