PUBLICATIONS OFFICE OF THE EUROPEAN UNION:�CELLAR, THE CENTRAL REPOSITORY OF THE EU

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LLM X LAW HACKATHON�Cambridge, UK�21 June 2025

SUMMARY

1. Presentation of the Publications Office of the EU
2. What is Cellar?
3. How is the data structured on Cellar?
4. Which data to retrieve in Cellar
5. APIs / Demos
6. Numbers

Publication Office: OUR MISSION�AND VISION

• make known to the public what the EU does and means and help to unlock the power of data
• ensure that information is available as accessible and reusable data
• facilitate transparency, economic activity and the diffusion of knowledge in all EU languages

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A well-informed EU, empowered by timely�and effective access�to trustworthy information and knowledge and benefiting from all the opportunities�this brings to society�and the economy

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Cellar

Dissemination: How can you use Cellar’s data?

CELL

CELLAR

Knowledge Graph

Content files

Technical data

Interfaces

Cellar: OP’s central data repository

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Cellar

OP’s central data repository

Digital content

Metadata

& semantics

Multilingual content

Machine-readable

Open to all citizens for retrieval and (re)use

Why Cellar exists?

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What do we publish?

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Content

Title, abstract, dates, subject, identifier, legal information etc.

...in different file

formats &

languages

Metadata

Data layers in Cellar

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Semantics

Structure and Formats

Knowledge Base

Knowledge

Graph

https://op.europa.eu/en/web/cellar/cellar-data

Linked Data and FAIR principles in CELLAR

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**https://www.go-fair.org/fair-principles/

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/S, SPARQL)
4. Include links to other URIs so that they can discover more things

Design Principles of Linked Open Data*

*https://www.w3.org/DesignIssues/LinkedData.html

Data structure

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manifestation_

manifests_expression

item_

belongs_to_

manifestation

expression_

belongs_to_work

Part 3: Data

Physical/digital file level – file itself

High-level concept, an intellectual or artistic creation, for example a specific Official Journal

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Language level; linguistic version of the work

Format level; a format of specific linguistic version of the work

http://publications.europa.eu/resource/oj/JOC_2022_182_R_0001

[…]oj/JOC_2022_182_R_0001.ENG

[…]oj/JOC_2022_182_R_0001.ENG.xhtml

[…]oj/JOC_2022_182_R_0001.ENG.xhtml.[…].doc.html

http://publications.europa.eu/resource/cellar/c686c133-cb43-11ec-b6f4-01aa75ed71a1

http://publications.europa.eu/resource/oj/JOC_2022_182_R_0001

http://publications.europa.eu/resource/celex/52022XC0504%2801%29

owl:sameAs

What can I retrieve in Cellar ?

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DIGITAL �CONTENT IN A �SPECIFIC LANGUAGE �& SPECIFIC FORMAT

RDF DESCRIPTION �OF A PUBLICATION

XML DESCRIPTION �OF A PUBLICATION

DESCRIPTION OF DIFFERENT PUBLICATIONS

How to retrieve content streams (digital files), for example a publication in PDF ?���

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http://publications.europa.eu/resource/{ps-name}/{psid}?{parameters} + header’s keys.

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https://op.europa.eu/en/web/cellar/cellar-data/publications

eng

fra

application/xhtml+xml

application/pdf;type=pdfa1a

http://publications.europa.eu/resource/oj/JOC_2022_182_R_0001

Accept:

…

Accept-language:

…

How to retrieve metadata of a publication ?���

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http://publications.europa.eu/resource/{ps-name}/{psid}?{parameters} + header’s keys.

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https://op.europa.eu/en/web/cellar/cellar-data/metadata/metadata-notices

application/rdf+xml;notice=tree

application/rdf+xml;notice=non-inferred-tree

application/rdf+xml

application/rdf+xml;notice=non-inferred

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http://publications.europa.eu/resource/oj/JOC_2022_182_R_0001

application/xml;notice=tree

…

rdf notice:

Accept:

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http://publications.europa.eu/resource/oj/JOC_2022_182_R_0001?decoding=en

xml notice:

Accept:

Accessing metadata using SPARQL?���

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http://publications.europa.eu/webapi/rdf/sparql

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https://op.europa.eu/en/web/cellar/cellar-data/metadata/knowledge-graph

prefix cdm: <http://publications.europa.eu/ontology/cdm#>

SELECT distinct ?act ?sig

where {

?c_act owl:sameAs ?act.

?c_act cdm:official-journal-act_date_publication "2023-10-02"^^<http://www.w3.org/2001/XMLSchema#date>

FILTER (regex(?act,'/oj/')).

?c_exp cdm:expression_belongs_to_work ?c_act.

?c_manif cdm:manifestation_manifests_expression?c_exp.

?c_sig cdm:signature_digital_signs_manifestation?c_manif.

?c_sig owl:sameAs?sig.

}

Should have to use API or VIRTUOSO to retrieve metadata?

API

• I want to extract the full direct metadata of a publication (I can also focus on a language or format)
• I want to extract the full inferred metadata of a publication

� I need to know the URL (cellar id or psi id) of the publication

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VIRTUOSO

• I want to list publications according to some criterias (collection, topic, format, etc.)
• I want to browse relations between publications
• I want to extract direct metadata of a publication

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Magnitude of data in Cellar

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~29 million hits per day in 2025

THANK YOU

emmanuelle.GAILLARD@publications.europa.eu

abdelfettah.FELIACHI@publications.europa.eu

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Annex

• SPARQL endpoint: https://publications.europa.eu/webapi/rdf/sparql
• Data structure documentation: https://op.europa.eu/en/web/cellar/cellar-data
• Knowledge graph (virtuoso) documentation: https://op.europa.eu/en/web/cellar/cellar-data/metadata/knowledge-graph
• Metadata API documentation: https://op.europa.eu/en/web/cellar/cellar-data/metadata/metadata-notices
• Digital content API documentation: https://op.europa.eu/en/web/cellar/cellar-data/publications
• Developers guide, end-user manual, postman queries: https://op.europa.eu/en/web/cellar/documentation

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EU LAW�eur-lex.europa.eu

• online access to EU and national law
• easily findable, accessible and transparent
• EUR-Lex, EU Law in Force, OP Portal and N-Lex
• over 2,000 easy-to-read summaries

EUROPEAN DATA�data.europa.eu

• open data news, studies, trends, stories, and academy
• data from EU institutions and public sector
• cca 1.9+ million datasets

EU TENDERS�ted.europa.eu

• transparency & access to business opportunities in the EU and beyond
• over 3,000 notices per day
• annual total value:�cca 815 billion EUR

• primary source of results from the projects funded by the EU's programmes for research and innovation
• foster open science, create innovative products and services and stimulate growth
• oldest EU website founded in 1994

EU RESEARCH RESULTS�cordis.europa.eu

EU PUBLICATIONS�op.europa.eu/publications

• reports, studies, information brochures, magazines and other publications from EU institutions, agencies and bodies
• ‘In your language’: publications in 24 official EU languages
• publications organised in thematic bundles

EU WHOISWHO�whoiswho.europa.eu

• The official directory of the EU
• Over 17,000 persons registered
• Contact details of all EU institutions, agencies and bodies (weekly updates)

EU VOCABULARIES�https://op.europa.eu/eu-vocabularies

• Ontologies, authority tables, thesaurus used in EU publications
• Easy and standardized way to publish
• Facilitates search and access to EU content
• Supports harmonization across languages and borders
• Powered by semantic technologies and interoperability principles

• Easy and standardized way to publish

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Three WEMI hierarchies in Cellar

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