RDF Schema
RDF Schema (Resource Description Framework Schema, variously abbreviated as RDFS, RDF(S), RDF-S, or RDF/S) is a set of classes with certain properties using the RDF extensible knowledge representation data model, providing basic elements for the description of ontologies. It uses various forms of RDF vocabularies, intended to structure RDF resources. RDF and RDFS can be saved in a triplestore, then one can extract some knowledge from them using a query language, like SPARQL.
| Resource Description Framework Schema | |
| Abbreviation | RDFS |
|---|---|
| Status | W3C Recommendation |
| Year started | January 5, 1999[1][2] |
| First published | April 30, 2002[2] |
| Latest version | 1.1 (Recommendation) February 25, 2014[3] |
| Organization | |
| Editors |
|
| Base standards | RDF |
| Related standards | |
| Domain | |
| Website | www |
The first version[1][4] was published by the World-Wide Web Consortium (W3C) in April 1998, and the final W3C recommendation was released in February 2014.[3] Many RDFS components are included in the more expressive Web Ontology Language (OWL).
Terminology edit
RDFS constructs are the RDFS classes, associated properties and utility properties built on the vocabulary of RDF.[5][6][7]
Classes edit
rdfs:Resource- Represents the class of everything. All things described by RDF are resources.
rdfs:Class- An rdfs:Class declares a resource as a class for other resources.
A typical example of an rdfs:Class is foaf:Person in the Friend of a Friend (FOAF) vocabulary.[8] An instance of foaf:Person is a resource that is linked to the class foaf:Person using the rdf:type property, such as in the following formal expression of the natural-language sentence: 'John is a Person'.
ex:John rdf:type foaf:Person
The definition of rdfs:Class is recursive: rdfs:Class is the class of classes, and so it is an instance of itself.
rdfs:Class rdf:type rdfs:Class
The other classes described by the RDF and RDFS specifications are:
rdfs:Literal- literal values such as strings and integers. Property values such as textual strings are examples of RDF literals. Literals may be plain or typed.
rdfs:Datatype- the class of datatypes.
rdfs:Datatypeis both an instance of and a subclass ofrdfs:Class. Each instance ofrdfs:Datatypeis a subclass ofrdfs:Literal. rdf:XMLLiteral- the class of XML literal values.
rdf:XMLLiteralis an instance ofrdfs:Datatype(and thus a subclass ofrdfs:Literal). rdf:Property- the class of properties.
Properties edit
Properties are instances of the class rdf:Property and describe a relation between subject resources and object resources. When used as such a property is a predicate (see also RDF: reification).
rdfs:domain- the rdfs:domain of an
rdf:Propertydeclares the class of the subject in a triple whose predicate is that property. rdfs:range- the rdfs:range of an
rdf:Propertydeclares the class or datatype of the object in a triple whose predicate is that property.
For example, the following declarations are used to express that the property ex:employer relates a subject, which is of type foaf:Person, to an object, which is of type foaf:Organization:
ex:employer rdfs:domain foaf:Person ex:employer rdfs:range foaf:Organization
Given the previous two declarations, from the triple:
ex:John ex:employer ex:CompanyX
can be inferred (resp. follows) that ex:John is a foaf:Person, and ex:CompanyX is a foaf:Organization.
rdf:type- a property used to state that a resource is an instance of a class. A commonly accepted QName for this property is "a".[9]
rdfs:subClassOf- allows declaration of hierarchies of classes.[10]
For example, the following declares that 'Every Person is an Agent':
foaf:Person rdfs:subClassOf foaf:Agent
Hierarchies of classes support inheritance of a property domain and range (see definitions in the next section) from a class to its subclasses.
rdfs:subPropertyOf- an instance of
rdf:Propertythat is used to state that all resources related by one property are also related by another. rdfs:label- an instance of
rdf:Propertythat may be used to provide a human-readable version of a resource's name. rdfs:comment- an instance of
rdf:Propertythat may be used to provide a human-readable description of a resource.
Utility properties edit
rdfs:seeAlso- an instance of
rdf:Propertythat is used to indicate a resource that might provide additional information about the subject resource. rdfs:isDefinedBy- an instance of
rdf:Propertythat is used to indicate a resource defining the subject resource. This property may be used to indicate an RDF vocabulary in which a resource is described.
RDFS entailment edit
An entailment regime defines, by using RDFS (or OWL, etc.), not only which entailment relation is used, but also which queries and graphs are well-formed for the regime. The RDFS entailment is a standard entailment relation in the semantic web.[11]
For example, the following declares that 'Dog1 is an animal', 'Cat1 is a cat', 'zoos host animals' and 'Zoo1 hosts the Cat2':
ex:dog1 rdf:type ex:animal ex:cat1 rdf:type ex:cat zoo:host rdfs:range ex:animal ex:zoo1 zoo:host ex:cat2
The graph is not well-formed because the system can not guess that a cat is an animal. To make a well-formed graph, the statement 'Cats are animals' can be added:
ex:cat rdfs:subClassOf ex:animal
Here is a correct example:
| In English | The graph |
|---|---|
| |
| RDF/turtle | |
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> . @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> . @prefix ex: <http://example.org/> . @prefix zoo: <http://example.org/zoo/> . ex:dog1 rdf:type ex:animal . ex:cat1 rdf:type ex:cat . ex:cat rdfs:subClassOf ex:animal . zoo:host rdfs:range ex:animal . ex:zoo1 zoo:host ex:cat2 . | |
If the triplestore (or RDF database) implements the regime entailment of RDF and RDFS, the SPARQL query as follows (the keyword "a" is equivalent to rdf:type in SPARQL):
PREFIX ex: <http://example.org/> SELECT ?animal WHERE { ?animal a ex:animal . } The following gives the result with cat1 in it, because the Cat's type inherits of Animal's type:
| animal |
|---|
<http://example.org/dog1> |
<http://example.org/cat1> |
<http://example.org/cat2> |
Examples of RDF vocabularies edit
RDF vocabularies represented in RDFS include:[10]
- FOAF: the source of the FOAF Vocabulary Specification is RDFS written in the RDFa syntax.[8]
- Dublin Core: RDFS source is available in several syntaxes[12]
- Schema.org: the source of their schema was originally RDFS written in the RDFa syntax until July 2020.[13][14]
- Simple Knowledge Organization System (SKOS) developed the RDF schema titled as SKOS XL Vocabulary, which is an OWL ontology for the SKOS vocabulary that uses the OWL RDF/XML syntax, and hence makes use of a number of classes and properties from RDFS.[15]
- The Library of Congress defines an RDF schema titled Metadata Authority Description Schema in RDF, or MADS/RDF for short. From the abstract, it is intended for use within their library and "information science (LIS) community". It allows for annotating special relational data, such as if an individual within a family is well-known via
madsrdf:prominentFamilyMember.[16] - The UniProt database has an RDF schema for describing biochemical data, and is specialized towards describing proteins.[17]
See also edit
- SPARQL Query Language for RDF
- Platform for Internet Content Selection (PICS)
- Resource Description Framework (RDF)
- Web Ontology Language (OWL)
- Semantic technology
- SHACL Shapes and Constraints Language for RDF
References edit
- ^ a b c Brickley, Dan; Guha, Ramanathan V.; Layman, Andrew, eds. (1998-04-09). "Resource Description Framework (RDF) Schemas". W3C. W3C Working Draft. RDF Schema Working Group. Retrieved 2021-04-23.
- ^ a b "RDF Schema 1.1 Publication History - W3C". W3C. n.d. Retrieved 2021-04-23.
- ^ a b Brickley, Dan; Guha, Ramanathan V., eds. (2014-02-25). "RDF Schema 1.1". W3C. 1.1. RDF Working Group. Retrieved 2021-04-23.
- ^ Bikakis N.; Tsinaraki C.; Gioldasis N.; Stavrakantonakis I.; Christodoulakis S., eds. (2012-03-21). (PDF). Archived from the original (PDF) on 2013-04-24. Retrieved 2021-04-23.
- ^ (PDF). csee.umbc.edu. UMBC's Department of Computer Science and Electrical Engineering. 2017. Archived from the original (PDF) on 2021-04-24. Retrieved 2021-04-24.
- ^ Lapalme, Guy (2002). . Université de Montréal. Archived from the original on 2021-01-14. Retrieved 2021-04-24.
- ^ Lagoze, Carl (2008-03-31). (PDF). Cornell University. Archived from the original (PDF) on 2019-07-12. Retrieved 2021-04-24.
- ^ a b Brickley, Dan; Miller, Libby, eds. (2014-01-14). "FOAF Vocabulary Specification 0.99". xmlns.com. The FOAF Project. Retrieved 2021-04-23.
- ^ DuCharme, Bob (2011). Learning SPARQL. Sebastopol, California, United States: O'Reilly Media. p. 36. ISBN 9781449306595.
- ^ a b Schreiber, Guus; Raimond, Yves; Manola, Frank; Miller, Eric; McBride, Brian, eds. (2014-06-24). "RDF 1.1 Primer". W3C. Working Group Note. RDF Working Group. Retrieved 2021-04-23.
- ^ Hayes, Patrick; McBride, Brian (2004-02-10). "RDF Semantics § 4.4 RDFS Entailment". W3C. RDF Core Working Group. Retrieved 2021-04-24.
- ^ Dublin Core Metadata Initiative (20 January 2020). "DCMI: DCMI Metadata expressed in RDF Schema Language". dublincore.org (published 2000). Retrieved 2021-04-23.
- ^ Schema.org (n.d.). . schema.org. Archived from the original on 2020-05-10. Retrieved 2021-04-24.
{{cite web}}: CS1 maint: unfit URL (link) - ^ Wallis, Richard (2020-07-17). "Informatively redirect accesses to retired file schema_org_rdfa.html · Issue #2656 · schemaorg/schemaorg". GitHub. Retrieved 2021-04-24.
- ^ Miles, Alistair; Bechhofer, Sean (2009-08-18). . Archived from the original on 2020-02-27. Retrieved 2021-04-24.
- ^ Library of Congress; et al. (MADS/XML community, MODS Editorial Committee) (n.d.). "MADS/RDF Primer". Library of Congress. Retrieved 2021-04-24.
- ^ UniProt (n.d.). "UniProt RDF schema ontology". UniProt. Retrieved 2021-04-24.
External links edit
- W3C RDFS Specification
- W3C RDF 1.1 Primer
- W3C SPARQL 1.1 Entailment Regimes Specification
- W3C RDFS Entailment
- SPARQL2XQuery Map OWL-RDF/S ontologies and XML Schemas. Transform XML Schema to OWL.