SPARCiTO is an OWL 2 DL ontology that enables the characterization of the nature or type of citations, both factually and rhetorically. Rather than treating all citations as equivalent, CiTO allows the relationship between a citing work and a cited work to be described with semantic precision -- distinguishing, for example, between citing a work as authoritative evidence, citing it to critique its findings, or citing it as background reading. It is part of the SPAR (Semantic Publishing and Referencing) Ontologies suite.
Background
CiTO was created by David Shotton and Silvio Peroni, with contributions from Paolo Ciccarese and Tim Clark. The original CiTO v1.6 introduced the core cito:cites property and its sub-properties. Version 2.0, a major revision, removed domain and range restrictions to permit independent use beyond conventional bibliographic citations, and spun out related entities into other SPAR ontologies (FaBiO, C4O, PSO). The ontology has evolved through numerous versions, with the current version 2.8.1 published on 16 February 2018.
Purpose and Scope
CiTO characterizes three kinds of citations:
- Direct and explicit: As in a reference list
- Indirect: A citation to a related paper by the same group on the same topic
- Implicit: Artistic quotations, parodies, or cases of plagiarism
The ontology defines the core property cito:cites and its inverse cito:isCitedBy, along with numerous sub-properties expressing specific citation intent such as citesAsAuthority, citesAsEvidence, critiques, extends, retracts, citesAsRecommendedReading, citesAsPotentialSolution, repliesTo, compiles, and speculatesOn.
Key Classes
Version 2.8 introduced a rich class hierarchy for self-citations:
| Class | Description |
|---|---|
| Citation | A reified citation with citing entity, cited entity, and characterization |
| SelfCitation | Citation where citing and cited entities share something significant |
| AuthorSelfCitation | At least one author in common |
| JournalSelfCitation | Same publication venue |
| FunderSelfCitation | Same funding agency |
| AffiliationSelfCitation | At least one author from same institution |
| AuthorNetworkSelfCitation | Co-authorship network link between authors |
Version History
The specification page documents a detailed changelog from v1.6 through v2.8.1, including the addition of citation act reification (v2.5), alignment with schema:citation (v2.6.4), the linksTo property (v2.7.0), and the self-citation class hierarchy (v2.8).
Serializations and Namespace
- Ontology IRI:
http://purl.org/spar/cito - Version IRI:
http://purl.org/spar/cito/2018-02-16 - Available in RDF/XML, Turtle, and N-Triples
- Imports the ODP Situation ontology (
situation.owl)
Governance and Maintenance
CiTO is maintained as part of the SPAR Ontologies by David Shotton and Silvio Peroni. It is distributed under a Creative Commons Attribution 4.0 International license. The source is hosted on GitHub.
Notable Implementations
CiTO is used in scholarly publishing workflows, citation analysis research, and linked data representations of bibliographic networks. It has been integrated with Schema.org via alignment to schema:citation.
Related Standards
- FaBiO (fabio): The FRBR-aligned Bibliographic Ontology, a companion SPAR ontology for describing bibliographic entities