Hunting for semantic clusters

Transcription

1 Hunting for semantic clusters Hierarchical structuring of Cultural Heritage objects within large aggregations Shenghui Wang 1 Antoine Isaac 2 Valentine Charles 2 Rob Koopman 1 Anthi Agoropoulou 2 Titia van der Werf 1 1 OCLC Research, Leiden, The Netherlands 2 Europeana Foundation, The Hague, The Netherlands TPDL 2013 Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( OCLC TPDL Research, 2013 Leiden, 1 / 24 T

2 Outline 1 Introduction 2 Hierarchically structuring CH objects based on levels of similarity 3 Results and evaluation Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( OCLC TPDL Research, 2013 Leiden, 2 / 24 T

3 Outline 1 Introduction 2 Hierarchically structuring CH objects based on levels of similarity 3 Results and evaluation Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( OCLC TPDL Research, 2013 Leiden, 3 / 24 T

4 Large-scale aggregators Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( OCLC TPDL Research, 2013 Leiden, 4 / 24 T

5 Search Europeana Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( OCLC TPDL Research, 2013 Leiden, 5 / 24 T

6 Duplicates Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( OCLC TPDL Research, 2013 Leiden, 6 / 24 T

7 Duplicates? Same objects, different providers Same page digitised three times Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( OCLC TPDL Research, 2013 Leiden, 7 / 24 T

8 Duplicates? Same objects, different providers Same page digitised three times henghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( OCLC TPDL Research, 2013 Leiden, 7 / 24 T

9 Challenges in large-scale aggregators Aggregation of metadata from heterogeneous collections leads to data quality issues (e.g., duplicates) henghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( OCLC TPDL Research, 2013 Leiden, 8 / 24 T

10 Challenges in large-scale aggregators Aggregation of metadata from heterogeneous collections leads to data quality issues (e.g., duplicates) Mapping from different formats and vocabularies to a shared data model may cause information missing (e.g., internal and external links between objects) henghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( OCLC TPDL Research, 2013 Leiden, 8 / 24 T

11 Challenges in large-scale aggregators Aggregation of metadata from heterogeneous collections leads to data quality issues (e.g., duplicates) Mapping from different formats and vocabularies to a shared data model may cause information missing (e.g., internal and external links between objects) Cultural Heritage objects could be linked differently (e.g., duplication, depiction/representation, derivation, succession, etc.) Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( OCLC TPDL Research, 2013 Leiden, 8 / 24 T

12 Challenges in large-scale aggregators Aggregation of metadata from heterogeneous collections leads to data quality issues (e.g., duplicates) Mapping from different formats and vocabularies to a shared data model may cause information missing (e.g., internal and external links between objects) Cultural Heritage objects could be linked differently (e.g., duplication, depiction/representation, derivation, succession, etc.) Keyword-based search does not provide end users a global overview of what is available. Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( OCLC TPDL Research, 2013 Leiden, 8 / 24 T

13 Outline 1 Introduction 2 Hierarchically structuring CH objects based on levels of similarity 3 Results and evaluation Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( OCLC TPDL Research, 2013 Leiden, 9 / 24 T

14 Hierarchical structuring based on levels of similarity Our method contains three parts: Fast clustering algorithm based on minhashes and compression similarity Field selection for focal semantic clusters Hierarchically structuring records based on similarity Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 10 Leiden, / 24 T

15 Fast clustering based on minhashes and compression similarity Two-step approach: Grouping records which could potentially be further clustered Transform metadata into a set of minhashes Group records with similar minhashes Iterative parallel clustering records based on compression similarity Select cluster heads which are far apart Greedily assign records to the closest cluster head Divide clusters if the clusters are not compact enough Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 11 Leiden, / 24 T

16 Fast clustering based on minhashes and compression similarity Two-step approach: Grouping records which could potentially be further clustered Transform metadata into a set of minhashes Group records with similar minhashes Iterative parallel clustering records based on compression similarity Select cluster heads which are far apart Greedily assign records to the closest cluster head Divide clusters if the clusters are not compact enough By varying the similarity level, clusters with different compactness can be produced. Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 11 Leiden, / 24 T

17 Focal semantic clusters At level 100, many clusters contains duplicates, or records with almost identical metadata. Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 12 Leiden, / 24 T

18 Focal semantic clusters At level 100, many clusters contains duplicates, or records with almost identical metadata. At level 80, many clusters are of specific interests, e.g., pages of the same book, pictures of the a same building, etc. Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 12 Leiden, / 24 T

19 Focal semantic clusters At level 100, many clusters contains duplicates, or records with almost identical metadata. At level 80, many clusters are of specific interests, e.g., pages of the same book, pictures of the a same building, etc. These focal semantic clusters often represent small cultural entities, which can be connected to other entities. Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 12 Leiden, / 24 T

20 Field selection for focal semantic clusters However, different data providers do not apply same standards in the same way. Same information could be put into different metadata fields The extent to which an object is described varies a lot provider by provider. Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 13 Leiden, / 24 T

21 Field selection for focal semantic clusters However, different data providers do not apply same standards in the same way. Same information could be put into different metadata fields The extent to which an object is described varies a lot provider by provider. Not all metadata fields should be used for clustering. Otherwise, the pages of one book are scattered in multiple clusters. Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 13 Leiden, / 24 T

22 Field selection for focal semantic clusters However, different data providers do not apply same standards in the same way. Same information could be put into different metadata fields The extent to which an object is described varies a lot provider by provider. Not all metadata fields should be used for clustering. Otherwise, the pages of one book are scattered in multiple clusters. We applied a standard Genetic Algorithm to automatically select the important fields which give the best focal clusters. Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 13 Leiden, / 24 T

23 Hierarchical structuring based on levels of similarity Level 100 Original G.A. Repr. Provider 1 Field selection 1 Provider 2 Field selection 2 Provider 3 Field selection 3 Level 80 Level 60 Level 40 level 20 Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 14 Leiden, / 24 T

24 Hierarchy example 20_651 40_ _ _ _ Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 15 Leiden, / 24 T

25 Outline 1 Introduction 2 Hierarchically structuring CH objects based on levels of similarity 3 Results and evaluation Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 16 Leiden, / 24 T

26 Experiments with a small dataset We applied the method on 1.1 million records from the UK. Manually check randomly chosen clusters and try to understand what made these records clustered together, i.e., identify the semantic links between records Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 17 Leiden, / 24 T

27 Categories of clusters Same objects/duplicate records Views of the same object Derivative works Parts of the same object Collections Thematic groupings henghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 18 Leiden, / 24 T

28 Categories of clusters Same objects/duplicate records Views of the same object Derivative works Parts of the same object Collections Thematic groupings Bowburn, boiler house henghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 18 Leiden, / 24 T

29 Categories of clusters Same objects/duplicate records Views of the same object Derivative works Parts of the same object Collections Thematic groupings henghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 18 Leiden, / 24 T

30 Categories of clusters Same objects/duplicate records Views of the same object Derivative works Parts of the same object Collections Thematic groupings Letter from Capt. John Livingston RAMC henghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 18 Leiden, / 24 T

31 Categories of clusters Same objects/duplicate records Views of the same object Derivative works Parts of the same object Collections Thematic groupings henghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 18 Leiden, / 24 T

32 Categories of clusters Same objects/duplicate records Views of the same object Derivative works Parts of the same object Collections Thematic groupings Rural life henghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 18 Leiden, / 24 T

33 Working with the full Europeana dataset 23.6M records from 2428 data providers across Europe (a data dump on Feb 2013) Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 19 Leiden, / 24 T

34 Working with the full Europeana dataset 23.6M records from 2428 data providers across Europe (a data dump on Feb 2013) At level 100, we found more than 200K clusters which contain highly similar records Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 19 Leiden, / 24 T

35 Working with the full Europeana dataset 23.6M records from 2428 data providers across Europe (a data dump on Feb 2013) At level 100, we found more than 200K clusters which contain highly similar records At level 80, we found nearly 1.5 million focal clusters from all individual data providers. Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 19 Leiden, / 24 T

36 Working with the full Europeana dataset 23.6M records from 2428 data providers across Europe (a data dump on Feb 2013) At level 100, we found more than 200K clusters which contain highly similar records At level 80, we found nearly 1.5 million focal clusters from all individual data providers. Similarity level #Records to be clustered #Clusters Time ,595, ,245 6m2.82s 80 23,595,555 1,476,089 * 60 6,407, ,268 3m35.26s 40 2,431, ,389 2m28.79s 20 1,068,188 84,554 1m20.99s Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 19 Leiden, / 24 T

37 Field selection for focal semantic clusters For the 10 providers with most records (covering 35% of the whole Europeana dataset), it took 161 minutes on average. Datasets with records cost 21 minutes on average. Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 20 Leiden, / 24 T

38 Field selection for focal semantic clusters For the 10 providers with most records (covering 35% of the whole Europeana dataset), it took 161 minutes on average. Datasets with records cost 21 minutes on average. #Providers metadata field dc:title dc:type dc:language dc:rights dc:subject (a) Top 10 most selected fields #Providers field combination dc:title 2 37 dc:title dc:type 3 28 dc:title dc:creator 4 23 dc:title dc:identifier 5 20 dc:description (b) Top 5 most selected field combinations Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 20 Leiden, / 24 T

39 Manual evaluation Randomly select 100 clusters at each level 7 evaluators categorised these clusters, based on the categories found in the first round Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 21 Leiden, / 24 T

40 Manual evaluation Randomly select 100 clusters at each level 7 evaluators categorised these clusters, based on the categories found in the first round Cluster Category Similarity Level Same objects/duplicate records Views of the same object Parts of an object Derivative works Collections Thematic grouping Nonsense Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 21 Leiden, / 24 T

41 Conclusions Finding similar CH objects is the first step towards identifying semantic links and groups of objects within large-scale aggregations. We developed a fast and scalable clustering algorithm, applied a Genetic Algorithm to select important fields and proposed an infrastructure to hierarchically structuring CH objects. Our evaluation shows the clusters at high similarity levels are usually accurate and useful, while those at lower levels need more investigation. Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 22 Leiden, / 24 T

42 Multidimensional similarities Eyre, James (Austrian National Library) Sir James Eyre ( ), Chief Justice of the Common Pleas (Government Art Collection) Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 23 Leiden, / 24 T

43 Multidimensional similarities Eyre, James (Austrian National Library) Sir James Eyre ( ), Chief Justice of the Common Pleas (Government Art Collection) Sir John Eardley Wilmot ( ) Chief Justice of the Common Pleas (Government Art Collection) Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 23 Leiden, / 24 T

44 Continue hunting for semantic clusters Thank you! Shenghui Wang Antoine Isaac Valentine Charles Rob Koopman Anthi Agoropoulou Titia van der Werf Shenghui Wang, Antoine Isaac, Valentine Charles, Rob Hunting Koopman, for semantic Anthi Agoropoulou, clusters Titia van der Werf ( TPDL OCLC2013 Research, 24 Leiden, / 24 T