Fusing semantic data
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Fusing automatically extracted annotations for the Semantic
WebAndriy NikolovKnowledge Media InstituteThe Open University
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Outline
• Motivation• Handling fusion subtasks
– problem-solving method approach
• Processing inconsistencies– applying uncertainty reasoning
• Overcoming schema heterogeneity– Linked Data scenario
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Database scenario
• Classical scenario (database domain)– Merging information from datasets
containing partially overlapping information
Name Year of birth E-mail Address
H. Schmidt 1972 [email protected] …
J. Smith 1983 [email protected] …
Name Year of birth E-Mail Job position
Wen, Zhao 1980 [email protected] …
Schmidt, Hans 1973 [email protected] …
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Database scenario
• Coreference resolution (record linkage)– Resolving ambiguous identities
Name Year of birth E-mail Address
H. Schmidt 1972 [email protected] …
J. Smith 1983 [email protected] …
Name Year of birth E-Mail Job position
Wen, Zhao 1980 [email protected] …
Schmidt, Hans 1973 [email protected] …
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Database scenario
• Inconsistency resolution– Handling contradictory pieces of data
Name Year of birth E-mail Address
H. Schmidt 1972 [email protected] …
J. Smith 1983 [email protected] …
Name Year of birth E-Mail Job position
Wen, Zhao 1980 [email protected] …
Schmidt, Hans 1973 [email protected] …
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Semantic data scenario
• Database domain:– A record belongs to a single
table– Table structure defines
relevant attributes– Inconsistency of values
• Semantic data:– Classes are organised into
hierarchies– One individual may belong
to several classes– Available properties depend
on the level of granularity– Other types of
inconsistencies are possible• E.g., class disjointness
foaf:Person
sweto:Person
foaf:namexsd:string
xsd:stringfoaf:mbox
sweto:Placesweto:lives_in
sweto:Organization
sweto:affiliated_with
sweto:Researcherxsd:stringsome:has_degree
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Motivating scenario – X-Media
RDF
Images
Other data
Annotation FusionText
Internal corporate reports (Intranet)
Pre-defined public sources (WWW)
Domain ontology
KnoFuss
Knowledge base
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Outline
• Motivation• Handling fusion subtasks
– problem-solving method approach
• Processing inconsistencies– applying uncertainty reasoning
• Overcoming schema heterogeneity– Linked Data scenario
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Handling fusion subtasks
• For each subtask, several available methods exist
• Example: coreference resolution– Aggregated attribute similarity
• [Fellegi&Sunter 1969]
– String similarity• Levenshtein, Jaro, Jaro-Winkler
– Machine learning• Clustering• Classification
– Rule-based
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Handling fusion subtasks
• All methods have their pros and cons– Rule-based
• High precision• Restricted to a specific domain
– Machine learning• Require sufficient training data
– String similarity• Lower precision• Still need configuration (e.g., distance metric, threshold, set of
attributes to include)
• Trade-off between the quality of results and applicability range – better precision requires more domain-specific knowledge
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Problem-solving method approach
• Fusion task is decomposed into subtasks• Algorithms defined as methods solving a particular
task• Each method is formally described using the fusion
ontology– Task handled by the method– Applicability criteria– Domain knowledge required– Reliability of output
• Methods are selected based on their capabilities
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KnoFuss architecture
Fusion KBIntermediate data
Main KB
KnoFuss
CoreferenceResolutionMethod
ConflictDetectionMethod
ConflictResolutionMethod
Method library
New data
Fusion ontology
• Method library– Contains implementation of each technique for specific
subtasks (problem-solving method [Motta 1999])• Fusion ontology
– Describes method capabilities– Defines intermediate structures (mappings, conflict sets, etc.)
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Task decomposition
Knowledge fusion
Coreferenceresolution
Knowledge base
updating
Modelconfiguration
Dependency identification
Dependency resolution
Linkdiscovery
Source KB
TargetKB
(fused)
TargetKB
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Method selection
Adaptive learning matcher Application context:
Publication
Application context:Journal Article
rdf:type owl:Thing
datatypeProperty ?x
reliability =0.4
rdf:type sweto:Publication
rdfs:label ?x
sweto:year ?y
reliability =0.8
rdf:type sweto:Article
rdfs:label ?x
sweto:year ?y
sweto:journal ?z
sweto:volume ?a
reliability =0.9
• Depends on:– Range of applicability– Reliability
• Configuration parameters– Generic (for individuals of unknown types)– Context-dependent
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Using class hierarchy
• Configuring machine-learning methods:– Using training instances for a subclass to learn
generic models for superclasses
owl:Thing
foaf:Person foaf:Document
sweto:Publication
sweto:Article sweto:Article_in_Proceedings
year
name
volume book_title
label
journal_name
Ind1: {label, year, book_title}Ind2: {label, year, book_title}Ind3: {label, year, book_title}
Ind1: {label, year}Ind2: {label, year}Ind3: {label, year}
Ind1: {label}Ind2: {label}Ind3: {label}
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Using class hierarchy
• Configuring machine-learning methods:– Combining training instances for subclasses to
learn a generic model for a superclasssweto:Publication
sweto:Article sweto:Article_in_Proceedings
year
volumebook_title
label
journal_name
Ind1: {label, year, book_title}Ind2: {label, year, book_title}Ind3: {label, year, book_title}
Ind1: {label, year}Ind2: {label, year}Ind3: {label, year}Ind4: {label, year}Ind5: {label, year}Ind6: {label, year}
Ind4: {label, year, journal_name, volume}Ind5: {label, year, journal_name, volume}Ind6: {label, year, journal_name, volume}
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Outline
• Motivation• Handling fusion subtasks
– problem-solving method approach
• Processing inconsistencies– applying uncertainty reasoning
• Overcoming schema heterogeneity– Linked Data scenario
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Data quality problems
• Causes of inconsistency– Data errors
• Obsolete data• Mistakes of manual annotators• Errors of information extraction algorithms
– Coreference resolution errors• Automatic methods not 100% reliable
• Applying uncertainty reasoning– Estimated reliability of separate pieces of
data– Domain knowledge defined in the ontology
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Refining fused data
• Additional evidence:– Ontological schema restrictions
• Disjointness• Cardinality• …
– Neighborhood graph• Mappings between related entities
– Provenance• Uncertainty of candidate mappings• Uncertainty of data statements• “Cleanness” of data sources
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Dempster-Shafer theory of evidence
• Bayesian probability theory:Assigning probabilities to atomic alternatives: – p(true)=0.6 ! p(false)=0.4 – Sometimes hard to assign– Negative bias:
Extraction uncertainty less than 0.5 – negative evidence rather than insufficient evidence
Dempster-Shafer theory: Assigning confidence degrees (masses) to sets of alternatives– m({true}) = 0.6– m({false}) = 0.1– m({true;false})=0.3
probability
support
plausibility
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Dependency detection
• Identifying and localizing conflicts– Using formal diagnosis [Reiter 1987] in
combination with standard ontological reasoning
ArticleArticle ProceedingsProceedings
Paper_10Paper_10
owl:disjointWithowl:disjointWith owl:FunctionalPropertyowl:FunctionalProperty
rdf:typerdf:type
hasYear2007
hasYear 2006
E. MottaE. Motta V.S. UrenV.S. UrenhasAuthor hasAuthor
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Belief networks (cont)
• Valuation networks [Shenoy and Shafer 1990]
• Network nodes – OWL axioms– Variable nodes
• ABox statements (I2X, R(I1, I2))
• One variable – the statement itself
– Valuation nodes• TBox axioms (XtY)• Mass distribution between several variables
(I2X, I2Y, I2XtY)
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Belief networks (cont)
• Belief network construction– Using translation rules– Rule antecedents:
• Existence of specific OWL axioms (one rule per OWL construct)
• Existence of network nodes– Example rule:
• Explicit ABox statements:IF I2X THEN CREATE N1(I2X)
• TBox inferencing:IF Trans(R) AND EXIST N1(R(I1, I2)) AND EXIST N2(R(I2, I3)) THEN CREATE N3(Trans(R)) AND CREATE N4(R(I1, I3))
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Example
#Paper_10#Paper_10
ArticleArticle ProceedingsProceedings
owl:disjointWithowl:disjointWith
rdf:type rdf:type
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Example
#Paper_10#Paper_10
ArticleArticle ProceedingsProceedings
owl:disjointWithowl:disjointWith
rdf:type rdf:type
#Paper_102Article
#Paper_102Proceedings
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Example
#Paper_10#Paper_10
ArticleArticle ProceedingsProceedings
owl:disjointWithowl:disjointWith
rdf:type rdf:type
#Paper_102Article
#Paper_102Proceedings
Article v :Proceedings
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Example
#Paper_102Article
#Paper_102Proceedings
Article v :Proceedings
m(true)=0.8m(false) = 0
m({true;false})=0.2
m(true)=0.6m(false) = 0
m({true;false})=0.4
#Paper_102 Article
#Paper_102 Proceedings
false false
false true
true false
true true
m( )=1.0
m( )=0.0
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Example
#Paper_102Article
#Paper_102Proceedings
Article v :Proceedings
m(true)=0.8m(false) = 0
m({true;false})=0.2
m(true)=0.6m(false) = 0
m({true;false})=0.4
#Paper_102 Article
#Paper_102 Proceedings
false false
false true
true false
false true
true false
m( )=0.15 -Dempster’s rule
m(
m(
)=0.23
)=0.62
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Example
#Paper_102Article
#Paper_102Proceedings
Article v :Proceedings
m(true)=0.62m(false) = 0.23
m({true;false})=0.15
m(true)=0.23m(false) = 0.62
m({true;false})=0.15
#Paper_102 Article
#Paper_102 Proceedings
false false
false true
true false
false true
true false
m( )=0.15
m(
m(
)=0.23
)=0.62
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Belief propagation
• Translating subontology into a belief network– Using provenance and confidence values of data statements– Coreferencing algorithm precision for owl:sameAs mappings
• Data refinement:– Detecting spurious mappings– Removing unreliable data statements
Articlev:in_Proc
Ind1=Ind2
Functional(year)
Article(Ind1)
(0.99;1.0)/(0.97;0.98)
in_Proc(Ind2) Ind1=Ind2
inProc(Ind1)
Ind1=Ind2
year(Ind1, 2007)
year(Ind2, 2007)
year(Ind1, 2006)
(0.9;1.0)/(0.74;0.82) (0.92;1.0)/(0.2;0.21) (0.85;1.0)/(0.72;0.85)
(0.95;1.0)/(0.91;0.96)
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Neighbourhood graph
• Non-functional relations: varying impact
Paper_10Paper_10 H. SchmidtH. SchmidthasAuthor
Paper_11Paper_11 Schmidt, HansSchmidt, Hans
owl:sameAs (0.9) owl:sameAs (0.3)
hasAuthor
ProceedingsProceedings
rdf:type
rdf:type
PersonPerson
GermanyGermany H. SchmidtH. Schmidtcitizen_of
GermanyGermany Schmidt, HansSchmidt, Hans
owl:sameAs (1.0) owl:sameAs (0.3)
citizen_of
CountryCountry
rdf:type
rdf:type
PersonPerson
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Neighborhood graph
• Implicit relations: set co-membership
Person11 = Person12
Person21 = Person22
Coauthor(Person12, Person22)
Person11 = Person12
Coauthor(Person11, Person22)
Person21 = Person22
Coauthor(Person21, Person22)
“Bard, J.B.L.”=“Jonathan Bard”
“Webber, B.L.”=“Bonnie L. Webber”
0.84/(0.86;1.0)
0.16/(0.83;1.0)1.0/(1.0;1.0)
1.0/(1.0;1.0)
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Provenance
• Initial belief assignments:– Data statements
(source AND/OR extractor confidence)
– Candidate mappings (precision of attribute similarity algorithms)
– Source “cleanness” – contains duplicates or not
Arl_Va Arl_Tx
Arlington = Arl_Tx
Arlington Arl_Tx
Arlington = Arl_Va
Arlington = Arl_Va
Arl_Va Arl_Tx
1.0/(1.0;1.0)
0.9/(0.31;0.35)
Arlington, Virginia
0.95/(0.65;0.69)
Arlington, Texas
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Experiments
• Datasets:– Publication 1
• AKT• Rexa• SWETO-DBLP
– Cora• database community benchmark• translated into RDF• 2 versions used
– different structure – different gold standard
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Experiments
Dataset No Matcher Publication
Prec. Recall F1 Prec. Recall F1
AKT/Rexa 1 Jaro-Winkler 0.950 0.833 0.887 0.969 0.832 0.895
2 L2 Jaro-Winkler 0.879 0.956 0.916 0.923 0.956 0.939
AKT/DBLP 3 Jaro-Winkler 0.922 0.952 0.937 0.992 0.952 0.971
4 L2 Jaro-Winkler 0.389 0.984 0.558 0.838 0.983 0.905
Rexa/DBLP 5 Jaro-Winkler 0.899 0.933 0.916 0.944 0.932 0.938
6 L2 Jaro-Winkler 0.546 0.982 0.702 0.823 0.981 0.895
Cora (I) 7 Monge-Elkan 0.735 0.931 0.821 0.939 0.836 0.884
Cora (II) 8 Monge-Elkan 0.698 0.986 0.817 0.958 0.956 0.957
• Publication individuals– Ontological restrictions mainly influence
precision
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Experiments
Dataset No Matcher Person
Prec. Recall F1 Prec. Recall F1
AKT/Rexa 7 L2 Jaro-Winkler 0.738 0.888 0.806 0.788 0.935 0.855
AKT/DBLP 8 L2 Jaro-Winkler 0.532 0.746 0.621 0.583 0.921 0.714
Rexa/DBLP 9 Jaro-Winkler 0.965 0.755 0.846 0.968 0.876 0.920
Cora (I) 10 L2 Jaro-Winkler 0.983 0.879 0.928 0.981 0.895 0.936
Cora (II) 11 L2 Jaro-Winkler 0.999 0.994 0.997 0.999 0.994 0.997
• Person individuals– Evidence coming from the neighborhood graph– Mainly influences recall
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Outline
• Motivation• Handling fusion subtasks
– problem-solving method approach
• Processing inconsistencies– applying uncertainty reasoning
• Overcoming schema heterogeneity– Linked Data scenario
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Advanced scenario
• Linked Data cloud: network of public RDF repositories [Bizer et al. 2009]
• Added value: coreference links (owl:sameAs)
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Data linking: current state
• Automatic instance matching algorithms– SILK, ODDLinker, KnoFuss, …
• Pairwise matching of datasets– Requires significant configuration
effort
• Transitive closure of links– Use of “reference” datasets
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Reference datasets
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Problems
• Transitive closures often incomplete– Reference dataset is incomplete– Missing intermediate links– Direct comparison of relevant datasets is
desirable
• Schema heterogeneity– Which instances to compare?– Which properties are relevant
A BReference
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Schema matching
• Interpretation mismatches– dbpedia:Actor = professional actor– movie:actor = anybody who participated in a movie
• Class interpretation “as used” vs “as designed”– FOAF: foaf:Person = any person– DBLP: foaf:Person = computer scientist
• Instance-based ontology matching
Repository Richard Nixon David Garrick
dbpedia:Actor DBPedia - +
movie:Actor LinkedMDB + -
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KnoFuss - enhanced
Knowledge fusion
Ontology integration
Knowledge base
integration
Ontology matching
Instancetransformation
Coreferenceresolution
Dependency resolution
Source KB
TargetKB
SPARQL query translation
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Schema matching
• Step 1: inferring schema mappings from pre-existing instance mappings
• Step 2: utilizing schema mappings to produce new instance mappings
Ontology 1 Ontology 2
Dataset 1 Dataset 2
Ontology 1 Ontology 2
Dataset 1 Dataset 2
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• Background knowledge:– Data-level
(intermediate repositories)
– Schema-level (datasets with more fine-grained schemas)
Overview
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Algorithm
• Step 1:– Obtaining transitive closure of
existing mappings
LinkedMDB DBPedia
movie:music_contributor/2490
MusicBrainz
music:artist/a16…9fdf
= =
dbpedia:Ennio_Morricone
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Algorithm
• Step 2: Inferring class and property mappings– ClassOverlap and PropertyOverlap mappings– Confidence (classes A, B) = |c(A)Åc(B)| / min(c(|A|), c(|B|))
(overlap coefficient)– Confidence (properties r1, r2) = |c(X)|/||c(Y)|
• X – identity clusters with equivalent values of r1 and r2• Y – all identity clusters which have values for both r1 and r2
LinkedMDB DBPediaMusicBrainz
music:artist/a16…9fdf
==
dbpedia:Ennio_Morriconemovie:music_contributor/2490
movie:music_contributor dbpedia:Artist
is_a is_a
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• Step 3: Inferring data patterns
• Functionality restrictions
• IF 2 equivalent movies do not have overlapping actors AND have different release dates THEN break the equivalence link
• Note:– Only usable if not taken
into account at the initial instance matching stage
Algorithm
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Algorithm
• Step 4: utilizing mappings and patterns– Run instance-level matching for individuals
of strongly overlapping classes– Use patterns to filter out existing mappings
• LinkedMDB
SELECT ?uri
WHERE {
?uri rdf:type movie:music_contributor .
}
• DBPediaSELECT ?uriWHERE { ?uri rdf:type
dbpedia:Artist . }
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Results
• Class mappings:– Improvement in recall
• Previously omitted mappings were discovered after direct comparison of instances
• Data patterns– Improved precision
• Filtered out spurious mappings• Identified 140 mappings
between movies as “potentially spurious”
• 132 identified correctly
00.10.20.30.40.50.60.70.80.9
1
Existing KnoFuss(only)
Combined
PrecisionRecallF1-measure
00.10.20.30.40.50.60.70.80.9
1
Existing KnoFuss(only)
Combined
PrecisionRecallF1-measure
00.10.20.30.40.50.60.70.80.9
1
Existing KnoFuss(only)
Combined
PrecisionRecallF1-measure
DBPedia/
DBLP
DBPedia/
LinkedMDB
DBPedia/
BookMashup
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Future work
• From the pairwise scenario to the network of repositories
• Combining schema and data integration in an efficient way
• Evaluating data sources– Which data source(s) to link to?– Which data source(s) to select data
from?
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Questions?
Thanks for your attention
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References
[Shenoy and Shafer 1990] P. Shenoy, G. Shafer. Axioms for probability and belief-function propagation. In: Readings in uncertain reasoning. San Francisco: Morgan Kaufmann, pp. 575-610, 1990
[Motta 1999] E. Motta. Reusable components for knowledge modelling. Amsterdam: IOS Press, 1999
[Bizer et al 2009] C. Bizer, T. Heath, T. Berners-Lee. Linked Data - the story so far. International Journal on Semantic Web and Information Systems 5(3), pp. 1-22, 2009
[Fellegi and Sunter 1969] Ivan P. Fellegi and Alan B. Sunter. A theory for record linkage. Journal of American Statistical Association, 64(328):1183-1210, 1969
[Reiter 1987] R. Reiter. A theory of diagnosis from first principles. Artificial Intelligence, 32(1):57-95, 1987