Linked Data Quality assessment applied and integrated to the Linked Data generation and publication workflow. Presented at the Data Quality tutorial, satellite event at SEMANTICS2016.

1. Mappings Validation
Data Quality Tutorial - SEMANTICS2016
Anastasia Dimou
Anastasia.Dimou@ugent.be ● @natadimou
Ghent University – iMinds

2. Linked (Open) Data
semantically annotated & interlinked data
using different vocabularies or ontologies
published in the form of RDF datasets

3. Linked (Open) Data
derive from originally heterogeneous
(semi-)structured data
e.g.
Eurostat from TSV
DBLP from DBLP database
DBpedia from Wikipedia
LinkedBrainz from MusicBrainz database
... … …

4. Linked Data Quality
in the context of Linked Data
generation and publication workflow

5. Linked Data Quality dimensions
Representational dimension
Intrinsic dimension
Accessibility dimension
Contextual dimension
A. Zaveri, A. Rula, A. Maurino, R. Pietrobon, J. Lehmann, and S. Auer.
Quality Assessment for Linked Data: A Survey.
Semantic Web Journal, 2016.

6. Linked Data Quality dimensions
Representational dimension
data modeling
Intrinsic dimension
Linked Data generation
Accessibility dimension
Linked Data publication
Contextual dimension
Linked Data consumption

7. Linked Data Quality dimensions
Representational dimension
data modeling
Intrinsic dimension
Linked Data generation
Accessibility dimension
Linked Data publishing
Contextual dimension
Linked Data consumption

8. Linked Data Quality - Intrinsic Dimension
determines the RDF Dataset Quality
by assessing it for possible violations
with respect to
accuracy (e.g. malformed datatype literals)
consistency (e.g. disjoint classes/properties)

9. Instead of applying Quality Assessment
to the already published Linked Data
as part of Linked Data consumption
Apply Quality Assessment
to the Mappings
that generate the Linked Data
as part of Linked Data production

10. Linked Dataset Quality Assessment (DQA)
Mappings Quality Assessment (MQA)
Mapping & Dataset Quality Assessment Workflow
Mappings & Quality Assessment Evaluation Results

11. Linked Dataset Quality Assessment (DQA)
Mappings Quality Assessment (MQA)
Mapping & Dataset Quality Assessment Workflow
Mappings & Quality Assessment Evaluation Results

14. dbo:Person

15. dbo:Personxsd:date

16. dbo:Personxsd:date
Linked Data Quality Assessment

17. Linked Data Quality Assessment (DQA)
RDFUnit http://rdfunit.aksw.org
test-driven data-debugging framework
based on SPARQL-patterns
D. Kontokostas, P. Westphal, S. Auer, S. Hellmann, J. Lehmann, R. Cornelissen, and A. J. Zaveri
Test-driven evaluation of linked data quality.
In Proceedings of the 23rd International Conference on World Wide Web

18. DQA with RDFUnit
…WHERE { ?resource %%P1%% ?c.
FILTER (DATATYPE(?c) != %%D1%%) }
…WHERE { ?resource dbo:birthDate ?c.
FILTER (DATATYPE(?c) != xsd:date) }

19. 10 domain violations
10 datatype violations

20. 1,000,000 domain violations!!!
1,000,000 datatype violations!!!

21. Linked Data Quality Assessment (DQA)
Similar violations occur repeatedly
within a single Linked Data set

22. Linked Data Quality Assessment (DQA)
Sets of triples of a dataset have
repetitive patterns

23. Linked Data Quality Assessment (DQA)
Sets of triples of a dataset have
repetitive patterns

24. DQA: Linked Data Quality Assessment
is applied by third parties
to already published Linked Data sets
violations
DQA

25. DQA: Linked Data Quality Assessment
Adjustments is NOT applied
at the root of the problem
violations
DQA

26. DQA: Linked Data Quality Assessment
Adjustments are overwritten
if a new version of the original data
is annotated and published as Linked Data
violations
DQA

27. Instead of applying Quality Assessment
to the already published Linked Data set
as part of data consumption

28. Apply Quality Assessment to the Mappings
that generate the Linked Data
A. Dimou, D. Kontokostas, M. Freudenberg, R. Verborgh, J. Lehmann, E. Mannens, S. Helmann, R. Van De Walle
Assessing and Refining Mappings to RDF to Improve Dataset Quality.
In Proceedings of The Semantic Web - ISWC 2015

29. Linked Dataset Quality Assessment (DQA)
Mappings Quality Assessment (MQA)
Mapping & Dataset Quality Assessment Workflow
Mappings & Quality Assessment Evaluation Results

30. Mapping languages
formalize patterns into rules to generate
Linked Data from some original data

31. RDF Mapping Language (RML) http://rml.io
extends the W3C-recommended R2RML
specify the mapping rules to
generate Linked Data
from heterogeneous data sources
mapping rules are Linked Data sets too!
A. Dimou, M. Vander Sande, P. Colpaert, R. Verborgh, E. Mannens, and R. Van de Walle.
RML: A Generic Language for Integrated RDF Mappings of Heterogeneous Data.
In Proceedings of the 7th Workshop on Linked Data on the Web (LDOW2014), 2014.

32. RDF Mapping Language (RML) http://rml.io
<#Mapping>
rr:subjectMap [ rr:class dbo:Event
rr:template "http://example.com/{Name}" ] ;
rr:predicateObjectMap [ rr:predicate dbo:birthDate
rr:objectMap [ rml:reference "Birth" ; rr:datatype xsd:gYear ] ] .

33. RDF Mapping Language (RML) http://rml.io

34. data map doc
Mapping
Processor
RDF Mapping Language (RML) http://rml.io

35. data map doc
Mapping
Processor
violations
DQA
DQA: Linked Data Quality Assessment

36. data map doc
Mapping
Processor
violations
DQA
DQA: Linked Data Quality Assessment

37. data map doc
Mapping
Processor
violations
DQA
DQA: Linked Data Quality Assessment

38. data map doc
Mapping
Processor
violations
MQA
MQA: Mapping Quality Assessment

39. DQA with RDFUnit over RML
…WHERE { ?resource %%P1%% ?c.
FILTER (DATATYPE(?c) != %%D1%%) }
…WHERE { ?resource dbo:birthDate ?c.
FILTER (DATATYPE(?c) != xsd:date) }

40. D→MQA with RDFUnit over RML
…WHERE { ?resource %%P1%% ?c.
FILTER (DATATYPE(?c) != %%D1%%) }
…WHERE { ?resource dbo:birthDate ?c.
FILTER (DATATYPE(?c) != xsd:date) }

41. D→MQA with RDFUnit over RML
…WHERE { ?resource %%P1%% ?c.
FILTER (DATATYPE(?c) != %%D1%%) }
…WHERE { ?resource dbo:birthDate ?c.
FILTER (DATATYPE(?c) != xsd:date) }
<#Mapping>
rr:subjectMap [ rr:class dbo:Event
rr:template "http://example.com/{Name}" ] ;
rr:predicateObjectMap [ rr:predicate dbo:birthDate
rr:objectMap [ rml:reference "Birth" ; rr:datatype xsd:gYear ] ] .

42. D→MQA with RDFUnit over RML
…WHERE { ?resource %%P1%% ?c.
FILTER (DATATYPE(?c) != %%D1%%) }
…WHERE { ?resource dbo:birthDate ?c.
FILTER (DATATYPE(?c) != xsd:date) }
… WHERE {
?resource rr:predicateObjectMap ?poMap.
?poMap rr:predicate %%P1%%;
rr:objectMap ?objM.
?objM rr:datatype ?c.
FILTER (?c != %%D1%%) }
<#Mapping>
rr:subjectMap [ rr:class dbo:Event
rr:template "http://example.com/{Name}" ] ;
rr:predicateObjectMap [ rr:predicate dbo:birthDate
rr:objectMap [ rml:reference "Birth" ; rr:datatype xsd:gYear ] ] .

43. data map doc
Mapping
Processor
violations
MQA
MQA: Mapping Quality Assessment

44. MQA with RDFUnit over RML
…WHERE { ?resource %%P1%% ?c.
FILTER (DATATYPE(?c) != %%D1%%) }
…WHERE { ?resource dbo:birthDate ?c.
FILTER (DATATYPE(?c) != xsd:date) }
… WHERE {
?resource rr:predicateObjectMap ?poMap.
?poMap rr:predicate %%P1%%;
rr:objectMap ?objM.
?objM rr:datatype ?c.
FILTER (?c != %%D1%%) }
<#Mapping>
rr:subjectMap [ rr:class dbo:Event
rr:template "http://example.com/{Name}" ] ;
rr:predicateObjectMap [ rr:predicate dbo:birthDate
rr:objectMap [ rml:reference "Birth" ; rr:datatype xsd:gYear ] ] .
1 ONLY domain violations!!!
1 ONLY datatype violations!!!

45. data map doc
Mapping
Processor
violations
MDQA
MDQA:
Uniform Mapping & Dataset Quality Assessment

46. Linked Dataset Quality Assessment (DQA)
Mappings Quality Assessment (MQA)
Mapping & Dataset Quality Assessment Workflow
Mappings & Quality Assessment Evaluation Results

47. MQA: Mapping Quality Assessment
discover not only the violations
but also their origin
before they are even generated

48. MQA: Mapping Quality Assessment
easily apply structural adjustments
prevent same violations to
appear repeatedly over distinct entities
allow intuitively combining
different ontologies and vocabularies

49. data map doc
Mapping
Processor
violations
MDQA
MDQA:
Uniform Mapping & Dataset Quality Assessment

50. data map doc
Mapping
Processor
violations
MDQA
MDQA:
Uniform Mapping & Dataset Quality Assessment
<#Result>
rut:testCase rut:datatypeError
spin:violationRoot <#ObjectMap> ;
spin:violationPath rr:datatype ;
spin:violationValue xsd:gYear ;
rut:missingValue xsd:date .

51. data map doc
Mapping
Processor
Mapping
Refinementsviolations
MDQA
Uniform Mapping & Dataset
Quality Assessment Workflow

52. Correcting MQA violations with RML Editor

53. Correcting MQA violations with RML Editor

54. Correcting MQA violations with RML Editor

55. data map doc
Mapping
Processor
violations
MDQA
MDQA:
Uniform Mapping & Dataset Quality Assessment
<#Result>
rut:testCase rut:datatypeError
spin:violationRoot <#ObjectMap> ;
spin:violationPath rr:datatype ;
spin:violationValue xsd:gYear ;
rut:missingValue xsd:date .
DEL: <#ObjectMap> rr:datatype xsd:gYear.
ADD: <#ObjectMap> rr:datatype xsd:date.

56. MQA with RDFUnit over RML
<#Result>
rut:testCase rut:datatypeError
spin:violationRoot <#ObjectMap> ;
spin:violationPath rr:datatype ;
spin:violationValue xsd:float ;
rut:missingValue xsd:int .
DEL: <#ObjectMap> rr:datatype xsd:gYear.
ADD: <#ObjectMap> rr:datatype xsd:date.
DEL: <#SubjectMap> rr:class dbo:Event.
ADD: <#SubjectMap> rr:class dbo:Person.

57. MQA with RDFUnit over RML
<#Result>
rut:testCase rut:datatypeError
spin:violationRoot <#ObjectMap> ;
spin:violationPath rr:datatype ;
spin:violationValue xsd:float ;
rut:missingValue xsd:int .
DEL: <#ObjectMap> rr:datatype xsd:gYear.
ADD: <#ObjectMap> rr:datatype xsd:date.
<#Mapping>
rr:subjectMap [ rr:class dbo:Person
rr:template "http://example.com/{Name}" ] ;
rr:predicateObjectMap [ rr:predicate dbo:birthDate
rr:objectMap [ rml:reference "Birth" ; rr:datatype xsd:date ] ] .
DEL: <#SubjectMap> rr:class dbo:Event.
ADD: <#SubjectMap> rr:class dbo:Person.

58. data
new
map doc
map doc
Mapping
Processor
Mapping
Refinementsviolations
MDQA
(optional)
Uniform Mapping & Dataset
Quality Assessment Workflow

59. data
new
map doc
map doc
Mapping
Processor
Mapping
Refinementsviolations
MDQA
(optional)
Uniform Mapping & Dataset
Quality Assessment Workflow

60. Uniform Mapping & Dataset
Quality Assessment Workflow

61. Mapping Quality Assessment: Limitations

62. Mapping Quality Assessment: Limitations
certain test cases inevitably
require the complete Linked Data set

63. Mapping Quality Assessment: Limitations
certain test cases inevitably
require the complete Linked Data set
cardinality,
functionality,
symmetricity

64. Mapping Quality Assessment: Limitations
certain test cases inevitably
require the complete Linked Data set
cardinality,
functionality,
symmetricity
on Mappings defense:
more data issue
NOT affected by the mapping rules

65. Linked Dataset Quality Assessment (DQA)
Mappings Quality Assessment (MQA)
Mapping & Dataset Quality Assessment Workflow
Mappings & Quality Assessment Evaluation Results

66. Dataset Vs Mapping Quality Assessment
Number of Violations
*Dbpedia and DBLP D2RQ Mappings were translated to RML mappings
#violations - Quality Assessment
Dataset Assessment Mappings Assessment
DBpedia EN 3.2M 160
DBLP 8.1M 8
A. Dimou, D. Kontokostas, M. Freudenberg, R. Verborgh, J. Lehmann, E. Mannens, S. Helmann, R. Van De Walle
Assessing and Refining Mappings to RDF to Improve Dataset Quality.
In Proceedings of The Semantic Web - ISWC 2015

67. Dataset Vs Mapping Quality Assessment
Time
Dataset Quality Assessment Mappings Quality Assessment
size time size time
DBPedia EN 62M 16h 115K 11s
DBPedia NL 21M 1.5h 53K 6s
DBLP 12M 12h 368 12s
A. Dimou, D. Kontokostas, M. Freudenberg, R. Verborgh, J. Lehmann, E. Mannens, S. Helmann, R. Van De Walle
Assessing and Refining Mappings to RDF to Improve Dataset Quality.
In Proceedings of The Semantic Web - ISWC 2015

68. Mapping Quality Assessment
* http://mappings.dbpedia.org/validation
Live update of DBpedia Mapping Quality Assessment results every night! ☺
Mapping Quality Assessment
size time
DBpedia EN 115K 11s
DBpedia NL 53K 6s
DBpedia All 511K 32s
A. Dimou, D. Kontokostas, M. Freudenberg, R. Verborgh, J. Lehmann, E. Mannens, S. Helmann, R. Van De Walle
Assessing and Refining Mappings to RDF to Improve Dataset Quality.
In Proceedings of The Semantic Web - ISWC 2015

69. * http://mappings.dbpedia.org/validation
DBpedia Mappings Quality Assessment
A. Dimou, D. Kontokostas, M. Freudenberg, R. Verborgh, J. Lehmann, E. Mannens, S. Helmann
DBpedia Mappings Quality Assessment.
To be published in Proceedings of the 15th International Semantic Web Conference: Posters and Demos 2016
Live update of DBpedia Mapping Quality Assessment results every night! ☺

70. Linked Dataset Quality Assessment (DQA)
Mappings Quality Assessment (MQA)
Mapping & Dataset Quality Assessment Workflow
Mappings & Quality Assessment Evaluation Results

71. Violations
are related to the dataset's schema
(vocabularies or ontologies)
occur repeatedly
within a single RDF dataset
The situation aggravates the more
ontologies and vocabularies
are reused and combined

72. Linked Data Quality Assessment
shifted from data consumption
to data publication
integrated systematically
in the publishing workflow
violations are identified,
resolved and will not re-appear
Linked Data of higher Quality is generated!!!

73. Mappings Validation
Data Quality Tutorial - SEMANTICS2016
Anastasia Dimou
Anastasia.Dimou@ugent.be ● @natadimou
Ghent University – iMinds