An overview over different alternatives and opportunities of using Linked Data principles and datasets for federated access to distributed OER repositories. The talk was held at the ARIADNE/GLOBE convening (http://ariadne-eu.org/content/open-federations-2013-open-knowledge-sharing-education) at LAK 2013, Leuven, Belgium on 8 April 2013

1. Motivation
Data on the Web
Some eyecatching opener illustrating growth and or diversity of web data
Linked Data for Open Educational Data Sharing
and Repository Federation
Stefan Dietze
(L3S Research Center, DE, @stefandietze, http://purl.org/dietze)
Stefan Dietze 02/04/13

2. Linked Data
 De-facto standard for sharing data on the Web
 Vision: well connected graph of open Web data
rNews
 W3C standards (RDF, SPARQL) to expose data
 Persistent URIs to interlink datasets Media Geo
Ontology Ontology
Number of
Domain Triples % (Out-)Links %
datasets
Media 25 1,841,852,061 5.82 % 50,440,705 10.01 % Dublin
Core
Geographic 31 6,145,532,484 19.43 % 35,812,328 DBpedia
7.11 %
Government 49 13,315,009,400 42.09 % 19,343,519 Ontology
3.84 %
Publications 87 2,950,720,693 9.33 % 139,925,218 27.76 %
Cross-domain 41 4,184,635,715 13.23 % 63,183,065 12.54 %
Life sciences 41 3,036,336,004 9.60 % 191,844,090 38.06 %
FOAF FMA BIBO
User-generated
20 134,127,413 0.42 % 3,449,143 0.68 % Ontology
content
295 31,634,213,770 503,998,829
Gene
Ontology
Source: http://lod-cloud.net/state, September 2011

3. Option 1: LD for integration of heterogeneous APIs & data
Use case: biomedical education in
Metamorphosis+ Tailored (L)CMS plugins
=> http://metamorphosis.med.duth.gr/ => http://www.meducator3.net/
Data/services integration & retrieval/search APIs
?
Educational Web Resources

4. Option 1: LD for integration of heterogeneous APIs & data
 Approach: 1) On the fly queries via “SmartLink” (Linked Data registry execution engine for open APIs)
2) Data lifting from heterogeneous repositories using “SmartLink” API and lifting
specifications
3) Data enrichment (via DBpedia, Freebase, BioPortal) & clustering, eg to identify correlated
resources
 Goal: improvement of distributed (non-LD) data with public LOD vocabularies; tighter interlinking to
provide coherent graph of educational data (across disparate stores)
http://purl.org/smartlink  http://linkededucation.org/meducator
Data/services integration & retrieval/search APIs Linked Educational Resources
Schemas: OAI-DC, LOM, …
Formats: XML, JSON
Interfaces: OAI-PMH, REST, SOAP
Educational Web Resources

5. Option 1: LD for integration of heterogeneous APIs & data
LD vocabularies for disambiguation & clustering
<led:Resource-BBC-519215>
<led:title>…virus…</led:title>
db:Life …
Sciences </led:Resource-BBC-519215>
db:Disease
db:Viral
db:Human Infections
Papilloma Virus
<led:Resource-mEducator-2139393292> <led:Resource-OpenLearn-2139393292>
<led:title>Virtual patient 1002, <led:title>…viral…disease…</led:title>
infections & HPV</led:title> …
… </led:Resource-OpenLearn-2139393292>
</led:Resource-mEducator-2139393292>
Stefan Dietze 08/04/13

6. Option 1: LD for integration of heterogeneous APIs & data
Some issues/challenges
On-the-fly data integration, but issues wrt:
 Annotation and description overhead: data lifting requires well-defined lifting specs for each API
 Performance: distributed queries (multiple HTTP requests), on-the fly data lifting and processing
 Scalability: decrease of query performance with increasing amount of repositories and/or data
http://purl.org/smartlink  http://linkededucation.org/meducator
Data/services integration & retrieval/search APIs Linked Educational Resources
Schemas: OAI-DC, LOM, …
Formats: XML, JSON
Interfaces: OAI-PMH, REST, SOAP
Educational Web Resources

7. Option 2: large-scale data harvesting and LD-ification
Linked Data for automated cross-platform integration
LD and non-LD data
Step 1 – Alignment of types/properties
?
<dc:title> <akt:has-title>
OER VideoLecture
LinkedUniversities Publication
educational videos
Step 2 – Linking of resources
 6 million distinct (but linked) resources
 97 million RDF triples
 21.6 GB of data
 Schema: http://data.linkededucation.org/ns/linked-education.rdf
 SPARQL: http://data.linkededucation.org/request/linked-learning/sparql
Mathieu d‘Aquin, Stefan Dietze 12/03/13 7

8. Option 2: large-scale data harvesting and LD-ification
Linked Data for automated cross-platform integration
LD and non-LD data
Larger scale data processing, but issues wrt:
Step 1 – Alignment of types/properties
 Scalability and performance of data storage ?
<dc:title>
(potential solutions: applying distributed RDF storage, map/reduce etc) <akt:has-title>
OER VideoLecture
 Poor query performance (on large-scale datasets)
LinkedUniversities Publication
 Redundant data maintenance => periodic data imports
educational videos
Step 2 – Linking of resources
 Maintenance of different identifiers (in case of non-LD sources: URIs vs internal IDs)
 6 million distinct (but linked) resources
 97 million RDF triples
 21.6 GB of data
 Schema: http://data.linkededucation.org/ns/linked-education.rdf
 SPARQL: http://data.linkededucation.org/request/linked-learning/sparql
Mathieu d‘Aquin, Stefan Dietze 12/03/13 8

9. Option 3: dataset cataloging and query federation
LinkedUp approach [ http://linkedup-project.eu ]
 “LinkedUp/Linked Education cloud” as (expanded) subset of LOD cloud:
CKAN – “The DataHub” (http://datahub.io) for data collection in dedicated group “linked-education”
 Public RDF vocabulary of datasets (“Linked Education Catalog”)
(classification of datasets according to, eg, represented types, disciplines, data quality)
 Additional integration datasets: dataset links and coreferences => providing a unified view on
educational data => Linked Education Graph
 Infrastructure, unified (SPARQL) endpoint & APIs for distributed/federated querying
LinkedUp LinkedUp
 Dataset Catalog
 Data Interlinking & Correlation
Educational Datasets
Stefan Dietze 08/04/13

10. http://data.linkededucation.org/linkedup/catalog/
Linked Education Cloud & Catalog
http://datahub.io/group/linked-education

11. Option 3: dataset cataloging and query federation
Sparse knowledge / metadata about datasets
http://datahub.io/group/linked-education
http://datahub.io/dataset/lak-dataset
Resource Types?
Topics & disciplines?
Quality & availability?

12. Option 3: dataset cataloging and query federation
Co-occurence of (mapped) types
Stefan Dietze 08/04/13

13. Option 3: dataset cataloging and query federation
Dataset graph (according to type co-occurence)
Stefan Dietze 08/04/13

14. Option 3: dataset cataloging and query federation
Detection of topics and dataset DBpedia Category
similarities Total
Management 180
Academia 151
Top-ranked categories/topics
Social_sciences 131
in Linked Education Catalog &
Philosophy_of_science 125
their frequency
Design 120
Sociology_index 117
Systems_science 117
Anthropology 116
Universities_and_colleges 116
Economics 114
Scientific_method 111
Approach Cognitive_science 110
Systems 107
 Enriching sample Sociological_terms 104
resources from each Neuropsychological_assessment 100
dataset with DBpedia Concepts_in_metaphysics 96
entities/categories Developmental_psychology 93
 Linking resources to LOD Political_philosophy 89
entities & categories via Cybernetics 88
Education 87
Philosophy_of_education 86
Arts 77
Critical_thinking 73
Biology 71
Political_science_termsDietze
Stefan 02/04/13 71

16. Summary and outlook
Summary
 Different ways of using LD for federation of OER repositories
 Linked Education data catalog (http://linkedup-project.eu,
http://data.linkededucation.org/linkedup/catalog/): Linked Data-based catalog of open educational
datasets (gradual addition of metadata about, eg, types, topics etc)
 On the way: exposing non-LD educational data according to LD priniciples (eg LAK dataset)
Future work
 Data interlinking: complementary dataset of links between datasets and actual data/resources
 Query federation and dedicated APIs
 Exploitation in innovative educational scenarios and applications => LinkedUp Challenge
(http://linkedup-challenge.org)
 40.000 EUR price budget
 Large network of organisations in LD & TEL
 Dedicated data and support
 Series of affiliated events at major conferences
(www2013, ESWC2013, OKCON, LAK2013…)
Stefan Dietze 08/04/13

17. LAK Challenge / LA & Linked Data Tutorial
in a nutshell
http://www.solaresearch.org/events/lak/lak-data-challenge/
http://linkedu.eu/event/lak2013-linkeddata-tutorial/
Stefan Dietze

18. Thank you!
Contact
 http://purl.org/dietze | @stefandietze
See also (general)
 http://linkedup-project.eu
 http://linkedup-challenge.org
http://linkededucation.org
 http://linkeduniversities.org
See also (data)
 http://datahub.io/group/linked-education
 http://data.linkededucation.org/linkedup/catalog /
 http://www.solaresearch.org/resources/lak-dataset/
 http://datahub.io/dataset/meducator
Stefan Dietze 08/04/13