Abstract

This document defines a small set of properties that extend SKOS Simple Knowledge Organization System [SKOS-REFERENCE] and the ISO 25964 SKOS extension [ISO-THES].

The primary purpose of this work was focused on modeling specific needs for the SKOS representation of the microthesauri structure of the UNESCO Thesaurus in the context of the UNESKOS project [UNESKOS]. Additionally, properties to improve the efficiency of RDF consuming have been defined. Such consumption should assume that the RDF resources must be well connected by properties in order to discover data, without having to use SPARQL endpoints [SPARQL] or inference processes.

Other techniques like Concise Bounded Description [CBD], that apparently solves the problem, implies certain complexity both, in the generation of the graph and the RDF data consumpsion. This technique is referred to specific cases for the inclusion of descriptions of resources other than the requested by an application. This involves the definition of specific cases, both for the generation and processing of such graphs, depending on the requested resource.

The vocabulary described in this document offers a simple approach to solve the two ways links between Concepts, Collections, Concept Groups and Concept Schemes.

1. Namespace and Vocabulary

The UNESKOS namespace URI is:

The SKOS vocabulary is a set of URIs in the list below.

All URIs in the UNESKOS vocabulary are constructed by appending a local name (e.g., "contains") to the UNESKOS namespace URI.

The rdf vocabulary can be downloaded from here.

1. Properties

uneskos:contains

IRI: http://purl.org/umu/uneskos#contains

Domain: skos:ConceptScheme

Inverse of: skos:inScheme

Comment

The SKOS model define the skos:inScheme property as a mechanism to link a Concept with one or serveral Concept Schemes. However, SKOS does not include an inverse property that allows to define the elements that are contained by a Concept Scheme. Note that skos:contains have not a range and can be applied to relate a Concept Scheme with any resource.

Example

The graph below defines a Concept Scheme that contains a Collection.

<MyConceptScheme> rdf:type skos:ConceptScheme .
<MyCollection> rdf:type skos:Collection .
<MyConcept> rdf:type skos:Concept .
<MyConceptScheme> uneskos:contains <MyCollection> .
<MyConcept> skos:inScheme <MyConceptScheme> .

Note that uneskos:contains is an inverse property of skos:inScheme and therefore the statements below can be infered:

<MyCollection> skos:inScheme <MyConceptScheme> .
<MyConceptScheme> uneskos:contains <MyConcept> .

NOTE: It is not necessary the inclusion of uneskos:contains property between the Concept Schemes and the Concepts in the SKOS dataset. In the context of a well designed KOS, it is possible to find a path to any Concept of the KOS starting from the Concept Scheme and the Top Concepts. However, SKOS does not provide any element to discover (i.e.) the Collections of a KOS from the Concept Scheme. The property uneskos:contains covers this need.

uneskos:hasMainConcept

IRI: http://purl.org/umu/uneskos#hasMainConcept

Domain: skos:Collection

Range: skos:Concept

Inverse of: uneskos:mainConceptOf

Sub-property of: skos:member

Comment

This property allows to set certain Concepts as access points to the Collections. This is very usefull for micro-thesauri composed KOS because the domain of skos:hasTopConcept is skos:ConceptScheme and it does not include skos:Collection. An alternative approach is to define the access points to a Collection as the intersection of the Top Concepts of the Concept Scheme with the member Concepts of a Collection. However a more direct and explicit mechanism is the use of uneskos:hasMainConcept. In this sense, uneskos:hasMainConcept is for skos:Collections like skos:hasTopConcept is for skos:ConceptScheme.

Take in account that the use of unekos:hasMainConcept does not replace the use of skos:hasTopConcept. The purpose of uneskos:hasMainConcept (and other UNESKOS properties) is "walk" across the KOS using paths like this:

Concept Scheme → Collection → Main Concept → Concept

Example

The graph below defines a Concept Scheme that contains a Collection.

<MyCollection> rdf:type skos:Collection .
<MyConcept> rdf:type skos:Concept .
<MyCollection> uneskos:hasMainConcept <MyConcept> .

Note that uneskos:hasMainConcept is both, an inverse property of uneskos:mainConceptOf and a sub-property of skos:member and therefore the statements below can be infered:

<MyConcept> uneskos:mainConceptOf <MyCollection> .
<MyCollection> skos:member <MyConcept> .

skos:hasMicroThesaurus

IRI: http://purl.org/umu/uneskos#hasMicroThesaurus

Domain: skos:ConceptScheme

Range: iso-thes:ConceptGroup

Inverse of: iso-thes:microThesaurusOf

Comment

This property is proposed as a mechanism to discover the Concept Group(s)  that conform a Concept Scheme. Since the browing of a KOS starts from the Concept Scheme, uneskos:hasMicroThesaurus set the path to the iso-thes:ConceptGroup resources that belong to him.

Example

The graph below defines a Concept Scheme that contains a Micro-thesaurus.

<MyConceptScheme> rdf:type skos:ConceptScheme .
<MyMicroThesaurus> rdf:type iso-thes:ConceptGroup .
<MyConceptScheme> uneskos:hasMicroThesaurus <MyConceptGroup> .

Note that uneskos:hasMicroThesaurus is an inverse property of iso-thes:microThesaurusOf and therefore the statements below can be infered:

<MyConceptGroup> iso-thes:microThesaurusOf <MyConceptScheme> .

uneskos:mainConceptOf

IRI: http://purl.org/umu/uneskos#mainConceptOf

Domain: skos:Concept

Range: skos:Collection

Inverse of: uneskos:hasMainConcept

Sub-property of: uneskos:memberOf

Comment

Since SKOS does not provide any specific property to define the Collections to which a Concept belongs, the property uneskos:mainConcepOf connect a Concept with Collection/s.

Example

The graph below defines a Concept shows the collection to which the concept belongs:

<MyCollection> rdf:type skos:Collection .
<MyConcept> rdf:type skos:Concept .
<MyConcept> uneskos:mainConceptOf <MyCollection> .

Note that uneskos:mainConceptOf is both, an inverse property of uneskos:hasMainConcept and a sub-property of uneskos:memberOf and therefore the statements below can be infered:

<MyCollection> uneskos:hasMainConcept <MyConcept> .
<MyConcept> uneskos:memberOf <MyCollection> .

uneskos:memberOf

IRI: http://purl.org/umu/uneskos#contains

Domain: Unión of skos:Concept and skos:Colections

Range: skos:Collection

Inverse of: skos:member

Comment

The SKOS model define the skos:member property as a mechanism to identify the Concepts that conform a Collection. However, SKOS does not include an inverse property to identify the Collection(s) to which a Concept belong. This property allows to define links from the Concepts to its Collections.

Example

The graph below defines a Concept Scheme that contains a Collection.

<MyCollection> rdf:type skos:Collection .
<MyConcept> rdf:type skos:Concept .
<MyConcept> uneskos:memberOf <MyCollection> .

Note that uneskos:contains is an inverse property of skos:inScheme and therefore the statements below can be infered:

<MyCollection> skos:member <MyConcept> .


2. References

[CBD]
CBD - Concise Bounded Description, Patrick Stickler, Author, W3C Member Submission 3 June 2005, http://www.w3.org/Submission/2005/SUBM-CBD-20050603/. Latest version avalaible at http://www.w3.org/Submission/CBD/
[ISO-THES]
ISO 25964 SKOS Extension, Antoine Isaac and Johan De Smedt, Authors. 17 March 2015, http://pub.tenforce.com/schemas/iso25964/skos-thes/
[SPARQL]
SPARQL 1.1 Overview, The W3C SPARQL Working Group, W3C Recommendation 21 March 2013, http://www.w3.org/TR/2013/REC-sparql11-overview-20130321/. Latest version avalaible at http://www.w3.org/TR/sparql11-overview
[SKOS-REFERENCE]
SKOS Simple Knowledge Organization System Reference, Alistair Miles and Sean Bechhofer, Editors, W3C Recommendation 18 August 2009, http://www.w3.org/TR/2009/REC-skos-reference-20090818/. Latest version avalaible at http://www.w3.org/TR/skos-reference
[UNESKOS]
Proyecto UNESKOS. Avalaible at http://skos.um.es/vocabularios