Designing and developing vocabularies in RDF

DATA
SUPPORT
OPEN
Training Module 2.4
Designing and
developing RDF
vocabularies
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This presentation has been created by PwC
Authors:
Nikolaos Loutas, Michiel De Keyzer and Stijn
Goedertier
Presentation
metadata
Slide 2
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under SMART 2012/0107 ‘Lot
2: Provision of services for the
Publication, Access and Reuse of
Open Public Data across the
European Union, through
existing open data
portals’(Contract No. 30-CE-
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© 2014 European Commission
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Learning objectives
By the end of this training module you should have an understanding
of:
• What the best practices are for creating an RDF vocabulary for
modelling your data
• Where to find RDF vocabularies for reuse.
• How you can create your own RDF vocabulary.
• How to publish your RDF vocabulary.
• The process and methodology for developing semantic agreements
developed by the ISA Programme of the European Commission.
Slide 3

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Content
This module is about...
• The steps for modelling your data.
• How to reuse existing vocabularies to model your data.
• How to create new classes and properties in RDF.
• How and where to publish your RDF vocabulary so that it can be
reused by others.
Slide 4

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RDF Vocabulary
Slide 5
“A vocabulary is a data model comprising classes, properties and
relationships which can be used for describing your data and
metadata.”
• RDF Vocabularies are sets of terms used to describe things.
• A term is either a class or a property.
 Object type properties (relationships)
 Data type properties (attributes)

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What are classes, relationships and properties?
Class. A construct that represents things in the real and/or
information world, e.g. a person, an organisation, a concepts such as
“health” or “freedom”.
Relationship. A link between two classes; for the link between a
document and the organisation that published it (i.e. organisation
publishes document), or the link between a map and the geographic
region it depicts (i.e. map depicts geographic region). In RDF
relationships are encoded as object type properties.
Property. A characteristic of a class in a particular dimension such as
the legal name of an organisation or the date and time that an
observation was made.
Slide 6

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Examples of classes, relationships and properties
Slide 7
http://.../org/217279
8119
site
http://example.com/site
/1234
RegisteredOrganisation Address
Dahliastraat 24, 2160
Wommelgem“Nikè”
a a
fullAddresslegalName
ClassProperty
Relationship

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Model your data
How to reuse from other vocabularies, define your own
terms and publish and promote your vocabularies to
describe the data.
Slide 8

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6 steps for modelling your data
Start with a robust Domain Model developed following a
structured process and methodology.
Research existing terms and their usage and maximise reuse of
those terms.
Where new terms can be seen as specialisations of existing terms,
create sub class and sub properties.
Where new terms are required, create them following
commonly agreed best practice.
Publish within a highly stable environment designed to be
persistent.
Publicise the RDF schema by registering it with relevant
services.
Slide 9
1
See also:
https://joinup.ec.europa.eu/community/semic/document/
cookbook-translating-data-models-rdf-schemas
2
3
4
5
6

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Start with a robust Domain Model
Slide 10
1
class Domain Model
RegisteredOrganisation
- identifier
- name
- registrationDate
- status
- type
Address
- identifier
- fullAddress
- postcode
ContactPoint
- identifier
- name
- telephone
- email
- fax
- website
Activity
- identifier
- name
Certificate
- identifier
- name
location
organisationCertificate
contactInformation
organisationActivity

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Reuse existing terms and vocabularies
• General purpose vocabularies: DCMI, RDFS
• To name things: rdfs:label, foaf:name, skos:prefLabel
• To describe people: FOAF, vCard, Core Person Vocabulary
• To describe projects: DOAP, ADMS.SW
• To describe interoperability assets: ADMS
• To describe registered organisations: Registered Organisation
Vocabulary
• To describe addresses: vCard, Core Location Vocabulary
• To describe public services: Core Public Service Vocabulary
• To describe datasets: DCAT, DCAT Application Profile, VoID
Slide 11
2

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Creating application profiles
• Different domains have different requirements for domain-specific
semantics, e.g. classification concepts.
• Generic RDF vocabularies usually provides the core base classes needed
to allow extensions to add specific sub-class structures or classification
schemes as required.
• In such cases, reusers are encouraged to define application profiles
particular to an application domain by specifying (if required) sub-
classes, sub-properties and controlled vocabularies.
• For example,
 DCAT Application profile for data portals in Europe
 Registered Organization vocabulary as an application profile of the
Organization ontology.
Slide 12
See also:
joinup.ec.europa.eu/asset/dcat_application_profile/home

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Advantages of reuse
• Reuse greatly aids interoperability of your data
 Use of dcterms:created, for example, the value for which should be a data typed
date such as 2013-02-21^^xsd:date, is immediately processable by many machines.
If your schema encourages data publishers to use a different term and date format,
such as ex:date "21 February 2013" – data published using your schema will require
further processing to make it the same as everyone else's.
• Reuse adds credibility to your schema.
 It shows it has been published with care and professionalism, again, this promotes
its reuse.
• Reuse is easier and cheaper.
 Reusing classes and properties from well defined and properly hosted vocabularies
avoids your having to replicate that effort.
Slide 13

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You can find reusable RDF vocabularies on...
Slide 14
http://joinup.ec.europa.eu/
http://lov.okfn.org/

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Creation of sub-classes and sub-properties
• RDF schemas and vocabularies often include terms that are very
generic.
• By creating sub-class and sub-property relationships, systems
that understand the super property or super class may be able to
interpret the data even if the more specific terms are unknown.
• Do not create sub-classes and sub-properties simply to
allow you to use your own term for something that already
exists.
Slide 15
3

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Creation of sub-properties - example
The Registered Organization vocabulary defines three sub-properties of
org:classification: companyType, companyStatus and companyActivity.
Slide 16

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Defining a sub-property in RDF
<rdf:Property rdf:about="rov:companyType">
<rdfs:label xml:lang="en">company type</rdfs:label>
<rdfs:comment xml:lang="en" rdf:parseType="Literal">
This property records the type of company. Familiar types are SA, PLC, LLC,
GmbH etc. Each jurisdiction will have a limited set of recognised company
types and these should be used in a consistent manner using a skos:Concept
as described in the <a href="#skos:Concept">Code</a> Class.
</rdfs:comment>
<rdfs:isDefinedBy rdf:resource="http://www.w3.org/ns/regorg#"/>
<rdfs:range rdf:resource="skos:Concept"/>
<rdfs:subPropertyOf rdf:resource="org:classification" />
<dcterms:identifier>legal:companyType</dcterms:identifier>
</rdf:Property>
Slide 17

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Where new terms are required, create them
following commonly agreed best practices
 Classes begin with a capital letter and are always singular, e.g.
skos:Concept.
 Properties begin with a lower case letter, e.g. rdfs:label.
 Object properties should be verbs, e.g. org:hasSite.
 Data type properties should be nouns, e.g. dcterms:description.
 Use camel case if a term has more than one word, e.g.
foaf:isPrimaryTopicOf.
Slide 18
4

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Defining a new class - Organisation
<rdf:RDF
xmlns:rdfs=“http://www.w3.org/2000/01/rdf-schema#”
xmlns:org=“htpp://example.org/organisation-schema”>
<rdf:Class rdf:about=“org:Organisation">
<rdfs:label xml:lang="en">Organisation</rdfs:label>
<rdfs:comment xml:lang:”en”>
Legal entity that is registered in an official national or regional
register.
</rdfs:comment>
</rdf:Class>
Slide 19

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Defining a new property - registrationNumber
<rdf:RDF
xmlns:org=“htpp://example.org/organisation-schema”>
<rdf:Property rdf:about=“org:registrationNumber">
<rdfs:label xml:lang="en">registrationNumber</rdfs:label>
The number that a registered organisation receives upon registration
in the official register.
</rdfs:comment>
</rdf:Class>
Slide 20

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Defining domain and range restrictions
<rdf:RDF
xmlns:org=“htpp://example.org/organisation-schema”
xmlns:locn=“http://www.w3.org/ns/locn#”>
<rdf:Property rdf:about=“org:isLocated">
<rdfs:label xml:lang="en">isLocated</rdfs:label>
The official address of the registered organisation’s headquarters.
</rdfs:comment>
<rdfs:domain rdf:resource=“org:Organisation”/>
<rdfs:range rdf:resource=“locn:Address”>
</rdf:Class>
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http://example.org/org/1234 org:isLocated http://dbpedia.org/page/Brussels

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Publish within a highly stable environment
designed to be persistent
• Choose a stable namespace for your RDF schema (e.g. W3C, Purl...)
• Use good practices on the publication of persistent Uniform
Resource Identifiers (URI) sets, both in terms of format and of their
design rules and management.
• Examples:
 http://www.w3.org/ns/adms
 http://purl.org/dc/elements/1.1
Slide 22
5
See also:
https://joinup.ec.europa.eu/community/semic/document/cookbook-translating-
data-models-rdf-schemas
http://www.slideshare.net/OpenDataSupport/design-and-manage-persitent-uris

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Publicise the RDF schema by registering it with
relevant services
Once your RDF schema is published you will want people to know about it. To
reach a wider audience register it Joinup and Linked Open Vocabularies.
Slide 23
6
Refinethesearch results via the
facetedsearch filters.
2
1
3
http://joinup.ec.europa.eu
http://lov.okfn.org

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Conclusions
Slide 24
Start with a robust Domain Model developed following a structured
process and methodology.
Research existing terms and their usage and maximise reuse of those
terms.
Where new terms can be seen as specialisations of existing terms, create
sub class and sub properties as appropriate.
Where new terms are required, create them following commonly agreed
best practice in terms of naming conventions etc
Publish within a highly stable environment designed to be persistent.
Publicise the RDF schema by registering it with relevant services.
Analyse
Model
Publish

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Group exercise
Slide 25
In groups of 2, create the RDF description of a vocabulary for
representing a citizen.
According to you, what are the main barriers to the reuse of
existing RDF vocabularies?
http://www.visualpharm.com
http://www.visualpharm.com
Take also the online test here!

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Thank you!
...and now YOUR questions?
Slide 26

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References
Slides 9:
• Linked Data Cookbook. W3C.
http://www.w3.org/2011/gld/wiki/Linked_Data_Cookbook
Slide 10-23:
• ISA Programme. Cookbook for translating Data Models to RDF Schemas.
https://joinup.ec.europa.eu/community/semic/document/cookbook-translating-
data-models-rdf-schemas
Slide 16, 18,-21:
• W3C. An organization ontology. http://www.w3.org/TR/vocab-org/
Slide 23:
• ADMS Brochure. ISA Programme.
https://joinup.ec.europa.eu/elibrary/document/adms-brochure
Slide 27

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Further reading
Linked Data Cookbook, W3C Government Linked Data Working
Group,
http://www.w3.org/2011/gld/wiki/Linked_Data_Cookbook
EC, ISA Process and methodology for developing semantic
agreements,
https://joinup.ec.europa.eu/community/core_vocabularies/documen
t/process-and-methodology-developing-semantic-agreements
EC ISA, Cookbook for translating Data Models to RDF Schemas
https://joinup.ec.europa.eu/community/semic/document/cookbook-
translating-data-models-rdf-schemas
Slide 28

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Related projects and initiatives
Joinup, http://joinup.ec.europa.eu
Linked Open Vocabularies (LOV), http://lov.okfn.org/
EC ISA, e-Government Core Vocabularies,
https://joinup.ec.europa.eu/community/core_vocabularies/home
W3C Schools – Learn RDF
http://www.w3schools.com/rdf/default.asp
EUCLID, http://euclid-project.eu/
XML Summer School http://xmlsummerschool.com/
Slide 29

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