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The Value of Usage Scenarios for Thesaurus Alignment in Cultural Heritage Context

The Value of Usage Scenarios for Thesaurus Alignment in Cultural Heritage Context. Antoine Isaac , Claus Zinn, Henk Matthezing, Lourens van der Meij, Stefan Schlobach, Shenghui Wang Cultural Heritage on the Semantic Web Workshop Oct. 12 th , 2007. Introduction. One important problem in CH

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The Value of Usage Scenarios for Thesaurus Alignment in Cultural Heritage Context

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  1. The Value of Usage Scenarios for Thesaurus Alignment in Cultural Heritage Context Antoine Isaac, Claus Zinn, Henk Matthezing, Lourens van der Meij, Stefan Schlobach, Shenghui Wang Cultural Heritage on the Semantic Web Workshop Oct. 12th, 2007

  2. OAEI 2007: Results from the Library Track Introduction • One important problem in CH • Heterogeneity of description resources • Thesauri (at large) • Classification schemes, subject heading lists … • Hampers access across collections

  3. OAEI 2007: Results from the Library Track Introduction Ontology alignment can help • Semantic links between ontology elements • o1:Cat owl:equivalentClass o2:Chat • Using automatic tools • E.g. exploiting labels, structure

  4. OAEI 2007: Results from the Library Track Introduction • Problem: not much on alignment applications • Need further research on context-specific alignment • Generation • Deployment • Evaluation • Important context dimension: application scenarios

  5. OAEI 2007: Results from the Library Track Agenda • Introduction • Dutch National Library Scenarios for Alignment • Book Re-indexing • Scenario-specific Evaluation

  6. OAEI 2007: Results from the Library Track KB and Thesaurus Alignement • National Library of the Netherlands (KB) • 2 main collections • Each described (indexed) by its own thesaurus • Problem: maintenance optimized wrt. redundancy/size?

  7. OAEI 2007: Results from the Library Track Usage Scenarios for Thesaurus Alignment at KB • Concept-based search • Retrieving GTT-indexed books using Brinkman concepts • Re-indexing • Indexing GTT-indexed books with Brinkman concepts • Integration of one Thesaurus into the other • Inserting GTT elements into the Brinkman thesaurus • Thesaurus Merging • Building a new thesaurus fro GTT and Brinkman • Free-text search • matching user search terms to both GTT or Brinkman concepts • Navigation: • browse the 2 collections through a merged version of the thesauri

  8. OAEI 2007: Results from the Library Track Agenda • Introduction • Dutch National Library Scenarios for Alignment • Book Re-indexing • Scenario-specific Evaluation

  9. OAEI 2007: Results from the Library Track The Book Re-indexing Scenario • Scenario: re-indexing of GTT-indexed books by Brinkman concepts

  10. OAEI 2007: Results from the Library Track The Book Re-indexing Scenario • If one of the thesauri is dropped, legacy data has to be indexed according to the other voc. • Automatically • Semi-automatically, users presented with candidate annotations

  11. OAEI 2007: Results from the Library Track Scenario Requirements • Mapping sets of GTT concepts to sets of Brinkman • alignreindex: {g1,…,gm} →{b1,…,bn} • Option where users select based on probabilities • Candidates concepts are given weights (e.g. [0;1]) • alignreindex’: {g1,…,gm} →{(b1,w1),…,(bn,wn)} • Generated index should be generally small • 99.2% of depot books indexed with no more than 3 Brinkman concepts

  12. OAEI 2007: Results from the Library Track Semantic Interpretation of Re-indexing Function 1-1 case: g1->b1 • b1 is semantically equivalent to g1 • OK • b1 is more general than g1 • Loss of information • Possible if b1 is the most specific subsumer of g1’s meanings • Indexing specificity rule

  13. OAEI 2007: Results from the Library Track Semantic Interpretation of Re-indexing Function Generic cases: combinations of concepts • Considerations on semantic links are the same • Combination matters Indexing is post-coordinated • {“Geography”; “the Netherlands”} in GTT -> book about geography of the Netherlands • Different granularities/indexing points of view • Brinkman has “Netherlands; Geography”

  14. OAEI 2007: Results from the Library Track Problem of Alignment Deployment Results of existing tools may need re-interpretation • Unclear semantics of mapping links • "=","<" • weights • Single concepts involved in mappings

  15. OAEI 2007: Results from the Library Track Example of Alignment Deployment Approach • Starting from similarity measures over both thesauri • sim(X,Y)=n • Aggregation strategy: simple Ranking • For a concept, take the top k similar concepts • Gather GTT concepts and Brinkman ones • Re-indexing function specified by conditions for firing rules • E.g., if the book indexing contains the left part of the rule

  16. OAEI 2007: Results from the Library Track Agenda • Introduction • Dutch National Library Scenarios for Alignment • Book Re-indexing • Scenario-specific Evaluation

  17. OAEI 2007: Results from the Library Track Evaluation Design • We do not assess the rules • We assess their application on book indexing • 2 classical aspects: • Correctness (cf. precision) • Completeness (cf. recall)

  18. OAEI 2007: Results from the Library Track Evaluation Design: Different Variants and Settings • Fully automatic evaluation • Using the set of dually indexed books as gold standard • Manual evaluation 1 • Human expert assesses candidate indices • Unsupervised setting: margin of error should be very low • Supervised setting: less strict, but size also matter • Manual evaluation 2 • Same as 1, but a first index has been produced by the expert • Distance between the two indices is assessed • Eventually changing original index

  19. OAEI 2007: Results from the Library Track Human Evaluation vs. Automatic Evaluation Taking into account • Indexing variability • Automatic evaluation compares with a specific indexing choice • Especially important if thesaurus doesn’t match book subject • Evaluation variability • Only one expert judgment is considered per book • Evaluation set bias • Dually-indexed books (may) present specific characteristics

  20. OAEI 2007: Results from the Library Track New Developments, Outside of Paper! • Reviews: you should add actual results of good general alignment systems as compared to your scenario • Ontology Alignment Evaluation Initiative • http://oaei.ontologymatching.org/2007 • State-of-the-art aligners applied to specific cases • This paper: grounding for an OAEI Library track • KB vocabularies • Evaluation in re-indexing scenario

  21. OAEI 2007: Results from the Library Track Automatic Evaluation • There is a gold standard for re-indexing scenario • General method: for dually indexed books, compare existing Brinkman annotations and new ones

  22. OAEI 2007: Results from the Library Track Automatic Evaluation • Book level: Precision & Recall for matched books • Books for which there is one good annotation • Minimal hint about users’ (dis)satisfaction • Annotation level: P & R for candidate annotations • Note: counting over annotations and books, not rules and concepts • Rules & concepts used more often are more important

  23. Notice: for exactMatch only OAEI 2007: Results from the Library Track Automatic Evaluation Results

  24. OAEI 2007: Results from the Library Track Manual Evaluation Method Variant 1, for supervised setting • Selection of 100 books • 4 KB evaluators • Paper forms + copy of books

  25. OAEI 2007: Results from the Library Track Paper Forms

  26. OAEI 2007: Results from the Library Track Annotation Transl.: Manual Evaluation Results Research question: quality of candidate annotations • Measures used: cf. automatic evaluation • Performances are consistently higher [Left: manual evaluation, Right: automatic evaluation]

  27. OAEI 2007: Results from the Library Track Annotation Transl.: Manual Evaluation Results Research question: evaluation variability • Krippendorff’s agreement coefficient (alpha) • High variability: overall alpha=0.62 • <0.67, classic threshold for Computational Linguistics tasks • But indexing seems to be more variable than usual CL tasks

  28. OAEI 2007: Results from the Library Track Annotation Transl.: Manual Evaluation Results Research question: indexing variability • Measuring acceptability of original book indices • Kripendorff’s agreement for indices chosen by evaluators • 0.59 overall alpha confirms high variability

  29. OAEI 2007: Results from the Library Track Conclusions • Better characterization of alignment scenarios is needed • For a single case there are many scenarios and variants • Requires to elicit requirements • And evaluation criteria

  30. OAEI 2007: Results from the Library Track Discussion: Differences between scenarios? • Concept-based search • Re-indexing • Integration of one thesaurus into the other • Thesaurus merging • Free-text search aided by thesauri • Navigation

  31. OAEI 2007: Results from the Library Track Discussion: Differences between scenarios? Semantics of alignment • A core of primitives that are be useful • broader/narrower, related • Some constructs are more specific • “AND” combination for re-indexing • Interpretation of equivalence? • Thesaurus merging: “excavation” = “excavation” • Query reformulation: “excavation” = “archeology; Netherlands”

  32. OAEI 2007: Results from the Library Track Discussion: Differences between scenarios? Multi-concept alignment • Useful for re-indexing or concept-based search • Less for thesaurus re-engineering scenarios • Combinations are not fully dealt with by thesaurus formats • But simple links involving a same concept can be useful • C1 BT C2 • C1 BT C3

  33. OAEI 2007: Results from the Library Track Discussion: Differences between scenarios? Precision and recall • Browsing -> emphasis on recall • For other scenarios, it depends on the setting Supervised vs. unsupervised

  34. OAEI 2007: Results from the Library Track Thanks!

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