12th of October, 2006 KEG seminar 1

Combining Ontology Mapping Methods Using Bayesian

NetworksOntology Alignment

Evaluation Initiative 2006 - 'Conference' Track

Ondřej ŠvábVojtěch Svátek

12th of October, 2006 KEG seminar 2

Overview

• Ontology Mapping

• Combining Ontology Mapping Methods

• Using Bayesian Networks– String distance metrics– Mapping patterns

• OAEI – Our track – conference domain– Evaluation

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Ontology Mapping

Ontology Mapping = discovering of Semantic correspondencies (equivalence, subsumption)

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Classification of ontology mapping techniques

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Modelling of interdependencies (1)

• Using Bayesian Networks• String distance metrics from SecondString

library (mapping methods)• Training data, pairs of concepts from ontologies

ekaw.owl a confOf.owl from OntoFarm collection– 798 pairs

• Bayesian network– nodes: mapping justification by each mapping method– Classification node: „align“ (true, false)

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Modelling of interdependencies (2)

• Two tested Bayesian Networks (two corresponding classifiers)– Naive Bayesian Structure

• Probability distributions learned from data

– Learned Bayesian Structure • Learned both CPT and structure

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Evaluation of models

• One-leave-out method (798x)

• Evaluation: precision, recall

• Precision more important than recall– 3:2 (precision weight 0,6), 4:1 (0,8)– C = P*a + R*b, kde a, b jsou váhy– higher C, better classifier

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73% precision, 60% recall, 88% accuracy at 80% threshold

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84% precision, 53% recall, 89% accuracy at 60% threshold

Align ci. CharJaccard, Monge-Elkan, Levenshtein | TFIDF, SmithWaterman, Jaccard, Jaro, SLIM

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Evaluation (c = P*a + R*b)

Naive bayes

Jaccard

BN 2

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Mapping patterns (1)

• Capturing structures using mapping patterns

• Mapping pattern between ontologies

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Mapping patterns (2)

Mapping pattern

Part of Bayesian Network

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Conclusions & Future works

• Combination of string-based methods is not promising• Implementation of low-level „string based justifications“

of mapping – suffix, prefix, identical names• Capturing context – Employ methods working with

structures of ontologies (graph-based), mapping patterns• Not only equivalence relations, but also discovery

subsumption relations – using linguistic sources, like WordNet

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Ontology Alignment Evaluation Initiative 2006 -

'Conference' Track

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OAEI 2006 at ISWC’06

• Evaluation initiative in Ontology matching• Since 2004• In 2006 OAEI workshop at Ontology matching

workshop, ISWC• Four tracks (six data sets)

– Benchmark (biblio), – Expressive ontologies: anatomy (2 ontologies 10k

classes), jobs (jobs and jobs seekers, real world case)– Directory (web sites directory) – 4 thousand

elementary test, Food data set– SKOS thesaurus about food with other food ontologies

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Conference track

• Coordinated by UEP

• Free exploration by participants within 10 ontologies

• Domain: conference organisation

• No a priori reference alignment

• Participants: 6 research groups

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Ontologies in track

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Participants (1)

• Combination of methods: lexicographic and contextual• ISLab

– 1:1 matching approach– Linguistic technique - thesaurus of terms and weighted

terminological relationships is exploited– Contextual technique - semantic relation in an ontology

• RiMOM– Ontology alignment defined as a directional one– Matchers: Name-based (also NLP methods), Instance-based,

Description-based, Taxonomy context-based, Constraints-based

• CtxMatch – DL formulas– Not only eq., also subsumption, disjointness, intersection

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Participants (2)

• COMA++– Extension of COMA

• Automs– Lexical matching method, LSI, structural

matching algorithm

• Falcon– elementary matchers: string-based, graph-

based

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Evaluation (1)

• Personal judgement of organisers

• interesting individual correspondences (inverse compound names, eg. PC_Member = Member_PC), synonyms

• Mapping errors: subsumption, inversion role, siblings, lexical confusion

• Mapping between relation and class, eg. has_an_email and E-mail

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Evaluation (2)

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Evaluation (3)

• Subsumption error– Author,Paper_Author– Conference_Trip, Conference_part

• Inversion role error– abstract_of_paper,reviewerOfPaper error

• Siblings– ProgramCommittee,Technical_commitee

• Lexical confusion error– program,Program_chair

• Relation – Class mapping– has_enddate,Date– hasTitle,Title; hasSurname,Surname

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Evaluation (4)

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Summary

• How to evaluate this track?– Interesting mappings

• Recall?