Hellmann keynote TKE (2016), Challenges, Approaches and Future Work for Linguistic Linked Open Data (LLOD) While the Linguistic Linked Open Data (LLOD) Cloud (http://linguistic-lod.org/) has evolved beyond expectations - thanks to the effort of a vibrant community - overall progress has to be seen under a more scrutinizing light. Initial challenges which have been formulated by Christian Chiarcos, Sebastian Nordhoff and me as early as 2011[1][2] have been discussed extensively in the LDL, MLODE and NLP & DBpedia workshop series and in several W3C community groups. In particular, the LIDER FP7 project (http://www.lider-project.eu/) - originally conceived to tackle these challenges and build a Linguistic Linked Open Data Cloud - rather gave them more shape and uncovered that there is yet quite a long road ahead to solve problems such as proper metadata, contextualisation of knowledge, data quality, hosting, open licensing and provenance, timely updated network links, knowledge integration and interoperability on the largest possible scale - the Web. The invited talk attempts to give a full account of these abovementioned challenges and presents and critically evaluates pertinent efforts and approaches including evolving standards such as the NLP Interchange Format (NIF)[3][4], DataID[5], SHACL[6], lemon[7] and the LIDER guidelines[8] as well as practical services such as LingHub[9], LODVader[10], RDFUnit[11] (just to mention a few). As a glimmer of hope, the talk will conclude with the recent efforts of the DBpedia community to coordinate the creation of a public data infrastructure for a large, multilingual, semantic knowledge graph, which is, of course, not a panacean golden hammer, but a potential step in the right direction to bridge the gap between language and knowledge. ________________ [1] Towards a Linguistic Linked Open Data cloud : The Open Linguistics Working Group (http://www.atala.org/IMG/pdf/Chiarcos-TAL52-3.pdf ) Christian Chiarcos, Sebastian Hellmann, and Sebastian Nordhoff. TAL 52(3):245 - 275 (2011) [2] Linked Data in Linguistics. Representing Language Data and Metadata (http://www.springer.com/computer/ai/book/978-3-642-28248-5 ) Christian Chiarcos, Sebastian Nordhoff, and Sebastian Hellmann (Eds.). Springer, Heidelberg, (2012) [3] http://persistence.uni-leipzig.org/nlp2rdf/ontologies/nif-core [4] https://www.w3.org/community/ld4lt/ [5] http://wiki.dbpedia.org/projects/dbpedia-dataid [6] http://w3c.github.io/data-shapes/shacl/ [7] https://www.w3.org/2016/05/ontolex/ [8] http://www.lider-project.eu/guidelines [9] http://linghub.lider-project.eu/ [10] http://lodvader.aksw.org/ [11] http://aksw.org/Projects/RDFUnit

1. Linguistic Linked Open Data
LLOD
Challenges, Approaches, Future Work
Sebastian Hellmann
TKE 2016
1

2. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
AKSW / KILT in Leipzig
Leipzig has become one of the largest Semantic Web centers
AKSW has 4 subgroups and 45 PhD students http://aksw.org/Team.html
Current position:
- Head of AKSW / KILT research group (8 PhD students)
- Knowledge Integration and Language Technology (KILT) http://aksw.org/Groups/KILT.html
- Project manager for 2 H2020 and 1 German research project (BMWi)
- http://freme-project.eu/ , http://aligned-project.eu/ , http://smartdataweb.de/
- Executive Director of the DBpedia Association http://dbpedia.org
2

3. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
Outline
● The vision behind Linked Data - a technological introduction
● Linguistic Linked Open Data
● Knowledge Modelling vs. Data Encoding
● LIDER
● Challenges and Approaches
3

4. Linked Data
4

5. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
Web of Data
WWW vs. GGG - https://en.wikipedia.org/wiki/Giant_Global_Graph
Data on the Web vs. the Web of Data vs. the Semantic Web
RDF - Entity Attribute Value - http://dbpedia.org/resource/Copenhagen
Three ways to publish RDF:
1. Linked Data: resource-level access via HTTP request (next slide)
2. SPARQL: query access via triplestore database
3. Dump: dataset-level access via bulk download
5

6. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
Linked Data
Four rules of https://www.w3.org/DesignIssues/LinkedData
1. Use URIs as names for things
2. Use HTTP URIs so that people can look up those names.
3. When someone looks up a URI, provide useful information, using the
standards (RDF*, SPARQL)
4. Include links to other URIs. so that they can discover more things.
https://en.wikipedia.org/wiki/Copenhagen vs.
http://dbpedia.org/resource/Copenhagen
Source: https://www.w3.org/DesignIssues/LinkedData.html
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7. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
Open Data != Open Data
Open Access vs Open License
Open Access means accessible like a web page (often unclear license)
http://opendefinition.org by OKFN:
“Knowledge is open if anyone is free to access, use, modify, and share it —
subject, at most, to measures that preserve provenance and openness.”
7

8. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
8
http://lod-cloud.net/

9. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
How is the Linked Data Cloud built?
9
- Open Access as the basis
- 50 links between things required to receive
a dataset link
- http://lov.okfn.org
- http://datahub.io
- Assessing Quantity and Quality of Links Between Linked Data Datasets by Cir
Sebastian Hellmann, Kay Müller, and Martin Brümmer in LDOW 2016 http://ev
org/ldow2016/papers/LDOW2016_paper_09.pdf

10. Linguistic Linked Open Data
10

11. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
Linguistic Linked Open Data
● Movement originated in the context of the Working Group for Open Data in
Linguistics (OWLG) at Open Knowledge Foundation (OKFN)
● Open is supposed to mean Open license
● Join community mailing list at http://linguistics.okfn.org/
● Current information at http://linguistic-lod.org/
maintained by John McCrae
-> Instructions on how to join the LLOD cloud
11

12. January 2011
12

13. 13
February 2012
Linked Data in Linguistics. Representing Language Data and Metadata (http://www.springer.
com/computer/ai/book/978-3-642-28248-5 ) Christian Chiarcos, Sebastian Nordhoff, and
Sebastian Hellmann (Eds.). Springer, Heidelberg, (2012)

14. August 2012
14

15. Sept 2012
MLODE
15
Special Issue on Multilingual Linked Open Data (MLOD)
Editors: Sebastian Hellmann, Steven Moran, Martin Brümm
and John McCrae,
Semantic Web, vol. 6, no. 4, pp. 315-317, 2015

16. Jan 2013
16

17. Sep 2013
17
LIDER FP7 EU Project
Start: Nov 2013
Duration: 2 years
http://lider-project.eu/

18. May 2014
18
LIDER FP7 EU Project
Start: Nov 2013
Duration: 2 years
http://lider-project.eu/

19. Nov 2014
19
LIDER FP7 EU Project
Start: Nov 2013
Duration: 2 years
http://lider-project.eu/

20. May 2015
20
LIDER FP7 EU Project
Start: Nov 2013
Duration: 2 years
http://lider-project.eu/

21. May 2016
21
LIDER FP7 EU Project
Start: Nov 2013
Duration: 2 years
http://lider-project.eu/

22. 22

23. Should we all use Linked Data?
23

24. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
Should we all use Linked Data?
When should we use linked data?
How should we use linked data?
When should we not use it?
24

25. Knowledge Modeling vs. Data Encoding
25

26. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
Entity Relationship Diagrams and UML
26
The Metadata Ecosystem of the
DataId Ontology, Markus
Freudenberg, submitted to MTSR
Conf 2016
http://dataid.dbpedia.org

27. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
XML encoding variants
27

28. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
XML encoding variants
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29. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
XML encoding variants
<same> should be symmetric, reflexive and transitive https://en.wikipedia.org/wiki/Equivalence_relation
Apples and oranges
29

30. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
Who can you ask what XML tags and structure
mean and what they are used for?
30

31. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
Who can you ask what XML tags and structure
mean and what they are used for?
31

32. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
Internationalization Tag Set (ITS) 2.0
http://www.w3.org/TR/its20/
● W3C Recommendation since 29 October 2013
● defines how to embed Machine Translation and Localisation
annotations, so called Data Categories, in (X)HTML and XML
● In addition to the human-readable document two ontologies are referenced
that capture the semantics of the standard.
● ITS Ontology as companion
● NLP Interchange Format (NIF) is the recommended format for RDF
conversion of ITS2.0 http://persistence.uni-leipzig.org/nlp2rdf/ontologies/nif-
core
32

33. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
Internationalization Tag Set (ITS) 2.0
33
One of the most efficient and robust ways to annotate HTML in a standardized manner

34. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
NLP Interchange Format 2.0 (old example)
34

35. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
NLP Interchange Format 2.0 (old example)
35

36. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
NIF 2.1 release pending
Join W3C Community Group: https://www.w3.org/community/ld4lt/
NIF useful for:
● Adding semantics to NLP tool output and corpora
● Providing and publishing identifiers for text and annotations
NIF is compact and scalable (cf. http://wiki-link.nlp2rdf.org/ ):
● Google Wikilinks Corpus with 10.6 million webpages and 31.5 million Wikipedia links (about 3 per
page) with a zipped size of 180 GB.
● 533 million triples (other formats 7-27% more)
● 79 GB (12 GB gzipped dumps) in Turtle format (original size 180 GB containing HTML markup)
36

37. LIDER
Towards a linguistic linked data ecosystem
37
Website: http://lider-project.eu
Guidelines: http://lider-project.eu/?q=guidelines

38. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
NIF
38

39. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
LIDER - Deliverable 2.1.2
39
http://www.lider-project.eu/sites/default/files/D2.1.2-Phase-II.pdf

40. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
LIDER Reference Architecture Deliverable 3.1.2.
General:
lemon - developed by
40
http://www.lider-project.
eu/sites/default/files/D3.1.2-v2.0.pdf

41. Challenges and Work in Progress
41

42. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
Identifier management
- Ideal identifiers are stable, i.e. the meaning behind the URI does not change
- Unrealistic for most use cases
- Easier for individuals, i.e. persons, organisations
- Non-trivial for terminology
Proposals:
1. Apply software development practices, i.e. versioning, update scripts http:
//vocol.org , http://github.org , http://aligned-project.eu
2. ??
42

43. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
Knowledge Fusion
- Linking is mostly done manual
- Linking 200 datasets pairwise requires maintenance of 40000 mappings
- Adding one after the other depends on the merge order
- Ideally we would be able to structure all datasets into clusters before linking
Proposals:
1. Under discussion with: Erhard Rahm - The Case for Holistic Data Integration
ADBIS 2016 Keynote: http://adbis2016.vsb.cz/keynote/ (to appear)
2. Apply software development processes: https://github.com/dbpedia/links
43

44. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
The Metadata Challenge
Where to publish metadata for your data?
- Barrier between data and dataset description
- Stale metadata
- Single point of truth missing
- Metadata too heterogeneous
- Download link missing
- No (sufficiently) complete view over the web of data possible, discovery failure
Proposals:
1. build an index: http://linghub.lider-project.eu/ (Clarin, LRE Map, Metashare, Datahub)
2. create a better schema: http://dataid.dbpedia.org and provide benefits for complying
44

45. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
MMoOn
- LIDER
- Lemon
- ODRL
- Olia
- NIF
- Morphology quite complex
- Specific to language and to the
linguist
- http://mmoon.org
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46. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
The Metadata Challenge 2
● RDF structure is too simple to keep additional metadata
○ Scope
○ Validity
○ Confidence
○ Technical metadata, i.e. collection time
Contextualisation is probably already better researched in lexicography than in Semantic Web.
46

47. Future work and take home messages
47

48. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
● Data Quality can be defined and measure with the tools.
● http://svn.aksw.org/papers/2014/WWW_Databugger/public.pdf Test-driven
Evaluation of Linked Data Quality by Dimitris Kontokostas, Patrick Westphal,
Sören Auer, Sebastian Hellmann, Jens Lehmann, Roland Cornelissen, and
Amrapali J. Zaveri in Proceedings of the 23rd International Conference on
World Wide Web
● Current standard:
○ https://www.w3.org/TR/shacl/
Data quality and verification
48

49. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
Open licenses in research
49
Are you willing to publish
your data under an open
license?
Can you make a product
out of your data?
No
Yes
Start
Congratulations, your paper
has been accepted
Yes
Good luck, we wish you all
the best and a high profit
No

50. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
Entity Linking Verification - new translator job profile
● http://www.freme-project.eu/
● Business Case: Integrating semantic enrichment into multilingual content in
translation and localisation
● In the future, translators and lexicographers
might be asked to judge entity linking and
verify data
50

51. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
Should I invest in publishing linked data?
Long-term data strategy, if you:
● Have many expected
inbound links
● Persistent ids
● Long term hosting and curation
Is no problem for you
-> yes (data value increases)
One time thing:
● Interest of externals only in the yellow zone
-> Publish under open license (let someone else do it)
51

52. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
DBpedia Association
DBpedia+
● Maintain identifier space
● Add open and member data to DBpedia+
● Add data following the LIDER guidelines
● Ability to add your backlinks
DBpedia Community meeting on the 15th of September in Leipzig
52

53. Sebastian Hellmann - AKSW/KILT Copenhagen TKE 2016
Events in 2016
● KEKI 2016 Workshop - Uses of Linguistic Linked Open Data http://keki2016.
linguistic-lod.org/ Deadline is 1st of July, but might be extended
● http://2016.semantics.cc
53

54. Thank you
hellmann@informatik.uni-leipzig.de
54