This presentation describes a solution on how to align well-know services with the aim of managing and harmonizing vocabularies' metadata, with a special use case on prefix.cc.

1. Harmonizing services for LOD
vocabularies: a case study
Ghislain Atemezing, Bernard Vatant,
Raphaël Troncy, Pierre-Yves Vanderbussche

2. Goal and Agenda
§ Goal: align services against Linked Open Vocabularies
to harmonize and manage vocabularies’ namespaces
§ Motivation
Ø Identify vocabularies using namespace
Ø Catalogs of vocabularies
§ Services managing vocabularies
Ø Prefix.cc versus LOV
Ø Different policies but same goal
§ Aligning LOV with Prefix.cc
§ Towards governance of vocabularies
2013/10/22
WaSABi Workshop, ISWC - 2013, Sydney
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3. Prefixes lookup headache
PREFIX.CC
What <wo> namespace stands for?
LOV
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4. QNames and vocabulary namespaces
§ Usage of namespaces
Ø From XML syntax with xmlns declarations
Ø Use to identify a valid namespace
§ On the Semantic Web
Ø Extended notion of namespace for other RDF
serialization (N3, Turtle)
Ø Some de facto prefixes emerging: rdfs:, foaf:, rdf: owl:
Ø SPARQL endpoints use a list of built-in prefixes not
transparent to the developers
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5. Why if … global use of prefixes
§ Global namespaces
Ø With good practices to
recommend a prefix
Ø Have a more transparent
list of built-in prefixes
Ø All the services
understand each other
with prefixes
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6. Accessing vocabularies
§ Catalogs of vocabularies
Ø Hosting vocabularies with search, review or download
features
Ø Curated manually or semi-automatically
§ Services
Ø Help finding vocabularies or detect namespaces
Ø Look up services: Prefix.cc, vocab.cc
Ø Triple-Checker, YASGUI
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7. Existing catalogs of vocabularies
Many overlapped of vocabularies among different catalogs
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8. LOV in a Nutshell : http://lov.okfn.org/dataset/lov/
§ A curated list of vocabularies
Ø More than 360 vocabularies
Ø Each of them described by vocabulary-of-a-friend
(voaf)
Ø Provide a dump in .n3 of the different versions of a
vocabulary
§ Some related services
Ø SPARQL endpoint: http://lov.okfn.org/endpoint/lov
Ø Search function: http://lov.okfn.org/dataset/lov/search
Ø An Aggregator endpoint: http://lov.okfn.org/endpoint/lov_aggregator
Ø An intelligent bot agent for updates:
http://lov.okfn.org/dataset/lov/bot
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9. LOV DESCRIPTION
CORE FEATURES OF THE FRAMEWORK
Domain
Intended Use
General
Promote and
facilitate the
reuse of
vocabularies in
the linked data
ecosystem.
Collection
Submitted by any
user via LOVSuggest tool.
Gatekeeping
Manual
curation and
automatic URI
validation
Number of
Ontologies
370
Dynamics
Growing
Search
metadata
Search
within
ontology
Yes, with
visual
depiction
Yes
Search across
ontologies
Navigation
criteria
Keyword-based;
structured
search (querybased)
Ordered by
prefix,
namespace,
title and
visual links
navigation
CORE FEATURES OF THE FRAMEWORK
Metrics
Comments
and review
Ranking
Reuse
popularity on
the LOD
Cloud
N/A - Only by
the curators
Metricbased
Web
service
access
SPARQL
endpoint
Content
available
Read/
Write
Ontology
directory
Ontology
registry
API
Yes
Ontology
metadata
, URI
Read
Yes
Yes
Applicatio
n platform
Yes
LOV DESCRIPTION WITH THE FRAMEWORK OF [d’Aquin-Noy2012-Survey]
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10. Prefix.cc in a Nutshell: http://prefix.cc
§ A service to look up vocabularies
Ø More than 1200 namespaces registered
Ø Anyone can add prefixes
Ø In case of conflicts, users can vote
§ Some related services
Ø Namespace lookup API: http://prefix.cc/about/api
Ø Reverse lookup API: http://prefix.cc/reverse
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11. LOV versus PREFIX.CC
Continuously growth of namespaces registered in prefix.cc.
Clearly view of the results of the harmonization process started in March,
2013
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12. Aligning LOV with Prefix.cc (1)
§ Scenarios
Ø Conflicts between prefix.cc and LOV
Ø Prefixes in LOV not present in prefix.cc
Ø URIs in prefix.cc that are actually LOV-able
vocabularies
§ Method
Ø Federated query in SPARQL 1.1
Ø Jena ARQ command line
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13. Aligning LOV with Prefix.cc (2)
§ Dealing with conflicts
Ø Clashes: same prefix but different URIs
Ø Disagreements on preferred namespace
§ Actions in case of disagreement
Ø Generally 4 types of actions
Ø Important: social aspect to contact the editors of the
vocabularies
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14. Vocabularies leading to contact editors
§ Contacting editors/maintainers
Ø Via social platforms: LinkedIn, Google+, Twitter, email
Ø Data retrieved mainly from vocabulary metadata.
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15. Finding Vocabularies in Prefix.cc
§ LOV check API: http://lov.okfn.org/dataset/lov/apidoc/
Ø Find out namespaces in Prefix.cc that are vocabularies
Ø Extract them as candidate vocabularies for LOV
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16. Some Results
Category
lov-­‐able
vocabs
Intersect-­‐prefixes
vocabs
in
LOV
vocabs
in
prefix.cc
Number
227
188
321
925
Findings
during
alignment
process
More than 200 prefixes are
vocabularies
14%
lov-­‐able
vocabs
11%
Intersect-­‐prefixes
vocabs
in
LOV
56%
19%
2013/10/22
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vocabs
in
prefix.cc
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17. Conclusion and Future Work
§ We have presented a way to manage prefixes
Ø By analyzing vocabularies in LOV and prefix.cc
Ø By providing mechanism of aligning two services dealing
with vocabulary prefixes
§ Future work
Ø Provide a unique interface for submission of namespaces
and prefixes to both services
Ø Publish a list of common recommended prefixes
Ø Foster and support current effort towards a more
sustainable governance of vocabularies.
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18. Thanks for your attention!
Q/A Session