CiTO, the Citation Typing Ontology

David Shotton (2010) Journal of Biomedical Semantics 1 (Suppl 1): S6. 

Additional File 2:  The CiTO Vocabulary and Definitions

Self-citation, provenance, copyright and license information

The URL of this document is

This document was written by David Shotton, Image Bioinformatics Research Group, Department of Zoology, University of Oxford (, and was last modified on 15 March 2010. 

© 2010 David Shotton.  This document is an open access reference work distributed under the terms of the Creative Commons Attribution License 2.5 (, which permits unrestricted use, distribution, and reproduction in any medium, provided that the original author and source are attributed.


The version of CiTO that this document describes is CiTO Version 1.6, published on 26 March 2010.  CiTO is written in the Web Ontology Language OWL, uses the namespace, and is available from  Version 1.3 of CiTO, the first public version, was published on 5 May 2009.  The ontology went through two further intermediate versions, Version 1.4 published on 24 November 2009. and Version 1.5 published on 1 February 2010, documentation of which are not separately published.  Changes between Versions 1.3 and 1.6 are detailed at the end of this document.


CiTO, the Citation Typing Ontology, is an ontology for describing the nature of reference citations in scientific research articles and other scholarly works, both to other such publications and also to Web information resources, and for publishing these descriptions on the Semantic Web.  This version of CiTO, CiTO Version 1.6, is described in the following paper for which this is Supplementary File S2:

Shotton, D (2010).  CiTO, the Citation Typing Ontology.  J. Biomedical Semantics 1 (Suppl 1): S6, doi:10.1186/2041-1480-1-S1-S6.

This supplementary file describes the CiTO Vocabulary in greater detail, giving a textual definition for each term in the annotation 'Comment' field. The terms names given below are the labels used for the object properties and classes in the Citation Typing Ontology, which are identical to the class and property names.  The definitions given in this document are identical to the textual definitions in CiTO itself. 


The namespace for CiTO is  The URI of each term in the ontology (e.g. cito:Book) is thus formed by using the term name preceded by '' (e.g.


The colours used for properties and classes in this document are the same as those employed in the first on-line example of CiTO’s use given at, which can be revealed by clicking on the “Turn Citation Typing On” button at the start of the References section. These colours, which are employed for convenience only, and have no semantic meaning other than to distinguish CiTO terms of different types, are:

Object Properties characterizing citations                                                                                          blue

Work and it sub-classes                                                                                                        pink

Expression and its sub-classes                                                                                            red

Manifestation and its sub-classes                                                                                      green

Data Property relevant to the Publication Status or Peer Review Status                          brown

Classes, Object Properties and Data Properties relevant to Citation Frequencies                    orange

Object Properties relating Work, Expression and Manifestation                                     black 

CiTO Object Properties:

Most of these relationships describe why a citing Work cites a cited Work. When using CiTO, a single citation should be described as having one or more of these relationships, which are both factual and rhetorical in nature.

cito:cites  A statement of fact that the citing Work cites the cited Work. [This is implicit in human-readable reference lists, and need not be stated when annotating them using CiTO.  However, the statement is useful in machine-readable metadata for construction of citation networks and other purposes.] [For scholarly Works, it is usually the final published Expression of the Work, known to publishers as the 'version of record', which is critical for CiTO, since it is the references within this version of record that are definitive, and it is the version of record itself that is cited by others.  However, for certain items such as a Database or a BlogEntry, it is the on-line Manifestation, i.e. the Web page URI, that is cited.  For this reason, the range of cito:cites is left unconstrained.  (Inverse property: cito:isCitedBy.)

cito:isCitedBy  A statement of fact that the cited Work is cited by the citing Work. (Inverse property: cito:cites.)

There are 21 subclasses of cito:cites, having the relationship from the citing Work A to the cited Work B (direction always A to B):

cito:citesAsAuthority  The citing Work refers to the cited Work as providing an authoritative description or definition of the subject under discussion.

cito:citesAsMetadataDocument  The citing Work refers to the cited Work as containing metadata about the citing Work. (Inverse property: cito:citesAsSourceDocument.)

cito:citesAsSourceDocument  The citing Work refers to the cited Work as the source about which the citing Work contains metadata. (Inverse property: cito:citesAsMetadataDocument.)

cito:citesForInformation  The citing Work refers the reader to the cited Work as a source of information on the subject discussed in the text.

cito:confirms  The citing Work confirms facts, ideas or statements presented in the cited Work.

cito:corrects  The citing Work corrects ideas or statements presented in the cited Work.

cito:credits  The citing Work acknowledges contributions made by the cited Work.

cito:critiques  The citing Work critiques facts, ideas or statements presented in the cited Work.

cito:disagreesWith  The citing Work disagrees with ideas or statements presented in the cited Work.

cito:discusses  The citing Work discusses facts, ideas or statements presented in the cited Work.

cito:extends  The citing Work extends facts, ideas or understandings presented in the cited Work.

cito:obtainsBackgroundFrom  The citing Work obtains background information from the cited Work.

cito:obtainsSupportFrom  The citing Work obtains intellectual or factual support from the cited Work.

cito:qualifies  The citing Work qualifies or places conditions upon facts, ideas or statements presented in the cited Work.

cito:refutes  The citing Work refutes ideas or statements presented in the cited Work.

cito:reviews  The citing Work reviews ideas or statements presented in the cited Work.

cito:sharesAuthorsWith  The citing Work has at least one author in common with the cited Work.

cito:supports  The citing Work provides intellectual or factual support for the cited Work.

cito:updates  The citing Work updates facts, ideas or understandings presented in the cited Work.

cito:usesDataFrom  The citing Work used data from the cited Work.

cito:usesMethodIn  The citing Work uses a method described in the cited Work.

CiTO Work, specifying the nature or type of a citing or cited Work, and its sub-classes     

cito:Work  As defined by FRBR (, a Work is a distinct intellectual or artistic creation - an abstract entity that is recognised through its various Expressions.  In CiTO, the definition of Work is restricted to Works that cite or are cited, primarily works of scholarship that contain bibliographic references, and excludes artistic works such as plays or photographs that do not.  For this reason cito:Work a subclass of frbr:Work.  Consequently, cito:Expression and cito:Manifestation are also made subclasses of their respective FRBR classes.

When using CiTO, a Work should be assigned to one of the following  41 disjoint sub-classes:

cito:Algorithm  A precise sequential set of pre-defined logical rules or computational operations to be employed for solving a particular problem in a finite number of steps. (Subclass of cito:Specification.)           

cito:AuthorityFile  A controlled vocabulary or official list that establishes, for consistency, the authoritative forms of headings, preferred terms or proper names to be used when creating a catalogue, or when indexing and searching a set of entities within a defined domain.  (Subclass of cito:Specification.)

cito:BiographicMetadata  Standard bibliographic metadata describing an Expression of a Work, including, to take the example of a Journal Article, the author(s), the date of publication, the title, the journal name and volume number, the first and last page numbers, and the Digital Object Identifier.  (Subclass of cito:Metadata.)

cito:Biography  An account of the events, works and achievements, personal and professional, during the life of a person, either living or dead.

cito:BookReview  A written Work consisting of a review and critical analysis of the content, scope and quality of a book or other monographic work.  (Subclass of cito:Review.)

cito:CaseForSupport  An accompaniment to a Grant Application that provides a description of a proposed project and gives reasons why it is worthy of funding. (See also cito:GrantApplication.)

cito:Catalog  A list of items describing the content of a resource, for example items in an exhibition, offered for sale by a vendor, or contained within a library or collection.  Ideally, Catalogs are created according to specific and uniform principles of construction and are under the control of an Authority File.  (Subclass of cito:Specification.)

cito:CitationMetadata  Metadata describing the citations made within an Expression of a Work to Expressions of other Works, and (optionally) some characteristics of the cited Expressions.  (Subclass of cito:Metadata.)

cito:ClinicalCaseReport  A presentation of findings following a clinical or medical investigation on a human or animal patient, that may contain a diagnosis and proposals for therapeutic treatment and/or epidemiological control measures, or may propose further evaluative studies that will eventually lead to such outcomes.  (Subclass of cito:Report.)

cito:ClinicalTrialDesign  A predefined written procedural method, designed to ensure reliability of findings, for undertaking a medical or veterinary clinical study of the safety, efficacy, or optimum dosage schedule of one or more diagnostic, therapeutic or prophylactic drugs or treatments, or of devices or techniques, involving a randomized controlled trial for evidence-based assessment in humans or animals, specifying criteria of eligibility, nature of controls, sampling schedules, data collection parameters, statistical analyses, reporting standards, etc. to be employed in undertaking the clinical trial.  (Subclass of cito:Specification.)

cito:ClinicalTrialReport  The report of a pre-planned medical or veterinary clinical study of the safety, efficacy, or optimum dosage schedule of one or more diagnostic, therapeutic or prophylactic drugs, or of devices, treatments or techniques, involving a randomized controlled trial for evidence-based assessment in humans or animals selected according to predetermined criteria of eligibility and observed for evidence of favourable and unfavourable effects.  (Subclass of cito:Report.)

cito:Dataset  A collection of related facts, often expressed in numerical form and encoded in a defined structure.

cito:EntityMetadata  Metadata describing the Work itself, including for example the name of the creator(s), the title, and the data and place of creation.  (Subclass of cito:Metadata.)

cito:ExperimentalProtocol  A predefined written procedural method, designed to ensure successful replication of results by others in the same or other laboratories, that describes the overall objectives, organization and implementation of a scientific experiment, and specifies the experimental design, experimental methods, reagents, instrumentation, sampling schedules, data collection parameters, statistical analyses, image processing procedures, safety precautions, reporting standards, etc. employed in undertaking the experiment.  (Subclass of cito:Specification.)

cito:GrantApplication  A formal written request for financial support from a grant-giving body in support of a project, for example an academic research project.  (See also cito:CaseForSupport.)

cito:InstructionalWork  A Work created for the purpose of education or instruction, such as a  text book, lecture, tutorial or instruction manual.

cito:Image  A visual representation other than text, including all types of cito:Moving Image and cito:Still Image.

cito:Metadata  A separate Work that provides information describing one or more characteristics of another Work or of an Expression of that Work.

cito:MinimalInformationStandard  A metadata standard specifying items to be included when creating metadata describing a dataset of a particular type, or when creating a structured digital abstract summarizing the main findings of an article or report in a particular domain of interest, thereby ensuring adequate descriptive information is recorded for subsequent resource discovery and/or interpretation of the information described.  (Subclass of cito:Specification.)

cito:Model  A mathematical, graphical or physical representation of some physical reality, conceptual idea or theoretical construct.

cito:MovingImage  A series of visual representations imparting an impression of motion when shown in succession.  Examples include animations, movies, television programs, videos, and computational simulations. (Subclass of cito:Image)

cito:NewsItem  An item of news.

cito:Ontology  A formal representation of a set of concepts within a domain of knowledge, and the relationships between those concepts.  (Subclass of cito:Specification.)

cito:Opinion  An expression of a personal or professional opinion on an issue or topic.

cito:Patent  A formal disclosure of a new invention approved by a government, made to record registration of intellectual property rights, and giving exclusive rights to the inventor or assignee to manufacture, use, licence or sell the invention for a certain number of years.

cito:PatentApplication  A formal disclosure of a new invention, made in application for a Patent.

cito:ProjectMetadata  Metadata describing the project that led to the creation of the Work, for example the project name, project institution and project funding information.  (Subclass of cito:Metadata.)

cito:Proposition  A proposal or proposition of a new conceptualization, hypothesis, idea or theory.

cito:ReferenceWork  A work  to which people refer for authoritative factual information, such as a dictionary, encyclopaedia, handbook or field guide, or certain types of informative web page, e.g. an institutional, research group or project home page.

cito:Report  A formal factual, methodological, statistical, technical or research report issued by an individual, group, agency, government body or other institution.

cito:ReportingStandard  A set of recommendations for the minimum reporting requirements to be employed when reporting a particular type of investigation or project, for example a randomized clinical trial, that may involve a checklist and a flow diagram, and that offers a standard way for authors to prepare complete and transparent reports of their findings, and aids their critical appraisal and interpretation of their data.  (Subclass of cito:Specification.)

cito:ResearchPaper  A report of original research findings.

cito:Review  A scholarly review of others’ work.

cito:Specification  An explicit description of, or set of requirements to be satisfied by a material, product resource, service or standard.

cito:StandardOperatingProcedure  Clear and detailed written instructions of a prescribed step-by-step procedure to be routinely followed and decisions to be made when undertaking a specific task, process or function, to achieve consistent performance, ensure safety and/or assure data quality.  (Commonly abbreviated "SOP".)  (Subclass of cito:Specification.)

cito:StillImage  A static visual representation, including diagrams, drawings, graphic designs, plans, maps, photographs and prints. (Subclass of cito:Image. Use where appropriate in preference to the superclass cito:Image.)

cito:Taxonomy  A classification arranged in a hierarchical structure of classes and subclasses, showing parent-child isA relationships, or broader_than - narrower_than relationships.  (Subclass of cito:Specification.)

cito:TechnicalStandard  An official or public specification or requirement for a technical method, practice, process or protocol involved in, for example, manufacturing, computation, electronic communication, or digital media.  (Subclass of cito:Specification.)

cito:Thesis  A Work consisting of formal presentations of research outputs submitted for examination in completion of a course of study at an institution of higher education, to fulfil the requirements for an academic degree.  [For the alternative meaning of the word "Thesis", namely a formulation of a concept, hypothesis, idea, point of view or theory presented for review and/or discussion, use cito:Proposition.]

 cito:Workflow  A recorded sequence of connected steps, which may be automated, specifying a reliably repeatable sequence of operations to be undertaken when conducting a particular project, for example an in silico investigation that extracts and processes information from a number of bioinformatics databases.  (Subclass of cito:Specification.)

cito:WorkingPaper  An unpublished paper, usually circulated privately among a small group of peers, to provide information or with a request for editorial improvement. 

CiTO Expression, specifying the nature or type of the Expression of a Work, and its sub-classes

cito:Expression  As defined by FRBR (, an Expression is the specific form that a Work takes each time it is 'realized' in physical or electronic form.  For CiTO, it is usually the final published Expression of the Work, known to publishers as the 'version of record', which is critical, since it is the references within this version of record that are definitive, and it is the version of record itself that is cited by others.  However, when citing Web Information Objects, it is their Manifestations that are normally the targets of the citations.

When using CiTO, an Expression should be assigned to one of the following 43 disjoint sub-classes:

cito:Abstract  A brief summary of a Work that gives an in-depth description or analysis of a particular subject (typically a Research Paper, Report, Review or Thesis), appearing at the beginning of the Work and designed to act as the point-of-entry that will help the reader quickly to obtain an overview of its contents.  (Subclass of cito:Document.)

cito:BlogEntry  Information manifested in a Blog, a type of WebPage comprising  periodic sequential entries containing commentary, descriptions of events, or other material such as images or videos, usually displayed in reverse-chronological order and usually maintained by an individual. (Subclass of cito:WebContent.)

cito:Book  A non-serial publication that is complete in one volume or a designated finite number of volumes.  A printed Manifestation of a book is often identified with an ISBN. (Subclass of cito:Document.)

cito:BookChapter  A defined chapter of a book, usually with a separate title or number. (Subclass of cito:BookSection.)

cito:BookSection  A defined section of a book, such as a preface, chapter or index, usually with a separate title or number. (Subclasses of cito:Document.)

cito:CaseForSupportDocument  An Expression of a Case for Support. (Usually associated with a Grant Application Document.)  (Subclasses of cito:Document.)

cito:ConferencePaper  A Research Paper, Review, Report or other work presented at a conference, seminar, symposium, workshop or similar event. (Subclasses of cito:Document.)

cito:ConferencePoster  A poster submitted for acceptance to and/or presented at a conference, seminar, symposium, workshop or similar event. (Subclasses of cito:Document.)

cito:ConferenceProceedings  A publication containing the programme and collected Conference Papers presented at a conference, seminar, symposium, workshop or similar event, or their Abstracts. (Subclasses of cito:Document.)

cito:Database  A structured collection of logically related records or data stored and retrieved using computer-based means.

cito:Document  An Expression of a Work conveying a body of information primarily in textual form.  A Document may contain one or more Figures and Tables in addition to text.

cito:Editorial  The Opinions of an editor expressed in a published Periodical Issue. (Subclass of cito:PeriodicalItem.)

cito:Email  A Personal Communication transmitted over the Internet as an item of electronic mail, typically based on the Simple Mail Transfer Protocol (SMTP).  (Subclasses of cito:Document.)        

cito:Figure  A visual communication object comprising one or more StillImages on a related theme.  If included within a publication, a Figure is typically unaligned with the main body of text, having its own descriptive textual figure legend.

cito:GrantApplicationDocument  An Expression of a Grant Application. (Usually associated with a Case For Support Document.) (Subclasses of cito:Document.)

cito:Journal  A scholarly Periodical primarily devoted to the publication of original Research Papers.  (Subclass of cito:Periodical.)

cito:JournalArticle  A Research Paper, Discussion, Opinion, Proposition or Review published in a scholarly Journal.    (Subclass of cito:PeriodicalItem.)  [Where the contribution is another type of journal item, e.g. an Editorial, News Item or Letter, use the disjoint class cito:JournalItem.]  

cito:JournalIssue  A particular published issue of a Journal, one or more of which will comprise a volume of the Journal.  (Subclass of cito:PeriodicalIssue.)

cito:JournalItem  An item in scholarly Journal, for example an Editorial, NewsItem,  Research Paper or Review. (Subclass of cito:PeriodicalItem.)

cito:Letter  A Personal Communication of a personal or professional nature between individuals and/or representatives of corporate bodies, typically in written or printed form and usually transmitted by the postal service or published in a Periodical.  In the latter case, the letter is typically addressed to the Editor and comments on or discussed an item previously published by that Periodical, or of interest to its readership.  (Subclasses of cito:Document.) 

cito:Magazine  A Periodical, usually devoted to a particular topic or domain of interest, and usually published weekly or monthly, consisting primarily of  non-peer reviewed Editorials, journalistic News Items and more substantive Articles, Reviews, Book Reviews and Discussions concerning current or recent events and publications, and matters of interest to the domain served by the Magazine.  Some scientific Journals, notably Science and Nature, also serve as science Magazines, containing substantive news reports and articles that that describe medical and scientific breakthroughs of vital or controversial importance.  (Subclass of cito:Periodical.)

cito:MagazineArticle  An article published in a Magazine, that is typically not peer-reviewed.  (Subclass of cito:PeriodicalItem.)

cito:MagazineIssue  A particular published  issue of a Magazine, identified by date, and sometimes also by place (e.g. "European edition") or language (e.g. "Spanish edition").  (Subclass of cito:PeriodicalIssue.)

cito:Manuscript  A textual Work prepared by hand, such as a typescript or word-processed pre-publication draft of a Research Paper or a Report, or a Work not otherwise reproduced in multiple copies. [cito:Manuscript is not intended to describe a handwritten historical document on paper or parchment, for which the distinction between Expression, Manifestation and Copy becomes blurred.] [See also cito:Preprint.] (Subclass of cito:Document.)

cito:Newspaper  A non-peer reviewed Periodical, usually published daily or weekly, consisting primarily of Editorials and News Items concerning current or recent events and matters of public interest.  (Subclass of cito:Periodical.)

cito:NewspaperArticle  An article written by a journalist and published in a Newspaper.  (Subclass of cito:PeriodicalItem.)

cito:NewspaperIssue  A particular published  issue of a Newspaper, identified by date, and sometimes also by place or time (e.g. "Late London Edition").  (Subclass of cito:PeriodicalIssue.)

cito:PatentApplicationDocument  The physical or electronic Expression of a Patent Application.  (Subclasses of cito:Document.)

cito:PatentDocument  The physical or electronic Expression of a Patent.  (Subclasses of cito:Document.)

cito:Periodical  A publication issued on a regular and ongoing basis, comprised of separate Editorials, Articles, News Items and/or other writings.

cito:PeriodicalIssue  A particular issue of a Periodical, identified and distinguished from other issues of the same publication by date and/or issue number and/or volume number. (Subclass of cito:Document.)

cito:PeriodicalItem  A piece of writing published in a Periodical, typically accompanied by other items by different authors. (Subclass of cito:Document.)

cito:PersonalCommunication  Information communicated personally from one individual to one or more another persons or organizations.

cito:Preprint  An author’s original scholarly Work as submitted to and/or accepted by a Journal for publication.  [For the version of the article published by the Journal and forming the ‘version of record’, use cito:JournalArticle.  See also cito:Manuscript.]  (Subclass of cito:Document.)  

cito:Presentation  A set of images of text and/or pictures used when communicating ideas or research results to an audience at a meeting, conference, symposium, seminar, lecture, workshop or other gatherings.

cito:PressRelease  A News Item published by an organization to provide information to journalists. (Subclass of cito:Document)

cito:ReportDocument  The embodiment of a Report, usually in printed form. (Use when the Report is not expressed in a Book, Book Section, Journal Item or other more specific form of Expression.)  (Subclasses of cito:Document.)

cito:Software  A computer program in source or compiled form, employing one or more Algorithms to execute a particular task.

cito:Spreadsheet  A computer file used for data storage that displays a grid of rows and columns, in which each cell can contain alphanumeric text, a numeric value, or a formula that defines how the content of that cell is to be calculated from the content of any other cell or cells.

cito:SupplementaryInformation  A document accompanying a published JournalArticle, containing additional information of relevance to the article, typically available from the publisher's web site via the JournalArticle itself. (Subclasses of cito:Document.)

cito:Table  A graphical means of presenting data in a grid of rows and columns, within which the cells usually contain alphanumeric text or numeric values.  If included within a publication, a table typically appearing unaligned with the main body of text, with its own descriptive title.

cito:WebContent  Information prepared specifically and primarily for manifestation in a WebPage, comprising Text, Images, Tables and/or other Works.

cito:WikiEntry  Information manifested in a Wiki, a type of WebPage that enables easy editing, usually maintained collaboratively by a project team, group or community to accumulate related information for shared use by the group, and for publication.  (Subclass of cito:WebContent.) 

CiTO Manifestation, specifying the Manifestation of an Expression  of a Work, and its sub-classes

cito:Manifestation  As defined by FRBR (, a Manifestation of an Expression of a Work defines its particular embodiment. cito:Manifestation specifically applies to electronic (digital) as well as to physical Manifestations of Expressions.  Examples of different Manifestations of a single 'version of record' Expression of a scholarly Work include an Article in a print Journal, the on-line version of that article as an HTML Web Page, and the downloadable PDF version of the same article, which can be seen as alternate 'containers' or 'channels' for the same information.

When using CiTO, a Manifestation of an Expression of a Work may be left unspecified, or may be categorized as belonging to one of  the following 5 disjoint sub-classes:

cito:ComputerFile  A block of digital information created by a computer system and stored electronically on a digital memory device in a form available for re-use, typically encoded in a particular format by a specific software application (e.g. in PDF, plain text, image, video or word processor file format).

cito:DigitalMediaFile  A Computer File stored off-line on a removable magnetic, optical, solid state or other digital storage device (e.g. a DVD, CD-ROM, DV tape, or USB flash drive) used to save, transport, distribute and play back such files. (Subclass of cito:ComputerFile.)

cito:OnlineFile  A Computer File stored on a computer attached to the Internet, available for viewing in a Web browser or for electronic transfer ('uploading' or 'downloading') to a second computer across the Internet. (Subclass of cito:ComputerFile.)

cito:PrintObject  A Manifestation of information in physical printed form, typically on paper.

cito:WebPage  A Manifestation of information on the World Wide Web, usually structured in HTML or XHTML format, identified by a Uniform Resource Identifier (URI), and made accessible to a user by means of the Hypertext Transport Protocol in a Web browser window.  Special software may enable a WebPage to be or to include a Blog or a Wiki.  Several interlinked WebPages hosted together on a Web server and accessed through a single domain name or IP address constitute a Web site. 

CiTO Data Property relevant to the Publication Status and Peer Review Status of the Expression of a Work

cito:peerReviewed  A Boolean data property having the value 'True' if the cited Work has been peer reviewed, or 'False' if the cited Work has not been peer reviewed.  [When using CiTO, the truth value of cito:peerReviewed may be left unspecified.] (Domain: cito:Expression.)

cito:unpublished  A Boolean data property having the value 'True' if the cited Work has not been published, or 'False' if the cited Work has been published.  [When using CiTO, the truth value of cito:Unpublished may be left unspecified.] (Domain: cito:Expression.)


CiTO Classes and Properties relevant to Citation Frequencies


cito:GlobalCitationCount  The number of times a Work has been cited globally, as determined from a particular bibliographic information source on a particular date.

cito:InTextCitationCount  The number of times a cited Work has been cited within the text of a citing Work.

Object Properties:

cito:globalCitationFrequency  The property linking an Expression of a Work to its Global Citation Count.

cito:globalCountSource  The URI of the bibliographic information source of information providing the Global Citation Count of a Work.

cito:inTextCitationFrequency  The property linking an Expression of a cited Work to its In-Text Citation Count within the citing Work.

cito:inTextCitationTarget  The URI of the cited Work for which the In-Text Citation Count is relevant. 

Data Properties:

cito:globalCountDate  The date on which the Global Citation Count of the Work was recorded from a named bibliographic information source.

cito:globalCountValue  An integer defining the value of the Global Citation Count of the Work recorded from a named bibliographic information source on a particular date.

cito:inTextCountValue  An integer defining the value of the In-Text Citation Count of the cited Work within the citing Work. 

CiTO Data Property relevant to Work, Expression and Manifestation

cito:isRealizationOf  As defined by FRBR (, the relationship between an Expression and the Work that is being expressed. (Domain: cito:Expression, Range: cito:Work.  Inverse property: cito:isRealizedThrough.)

cito:isEmbodimentOf  As defined by FRBR (, the relationship between a Manifestation and the Expression being manifested. (Domain: cito:Manifestation, Range: cito:Expression.  Inverse property: cito:isEmbodiedIn.)

cito:isEmbodiedIn  As defined by FRBR (, the relationship between an Expression of a Work and its Manifestation. (Domain: cito:Expression, Range: cito:Manifestation.  Inverse property: cito:isEmbodimentOf.)

cito:isRealizedThrough  As defined by FRBR (, the relationship between a Work and its Expression. (Domain: cito:Work, Range: cito:Expression.  Inverse property: cito:isRealizationOf.)



Changes between version 1.3 and version 1.6 of CiTO

3 New FRBR classes




9 New CiTO Object Properties







cito:isRealizedThrough             (Domain: cito:Work, Range: cito:Expression.  Inverse property: cito:isRealizationOf.)

cito:isRealizationOf                    (Domain: cito:Expression, Range: cito:Work.  Inverse property: cito:isRealizedThrough.)

cito:isEmbodiedIn                       (Domain: cito:Expression, Range: cito:Manifestation.  Inverse property: cito:isEmbodimentOf.)

cito:isEmbodimentOf                  (Domain: cito:Manifestation, Range: cito:Expression.  Inverse property: cito:isEmbodiedIn.)

1 New CiTO Data Property

cito:unpublished                         (Domain: cito:Expression.)

Change to CiTO Object Properties and Data Properties

Domain and range restrictions removed on cito:cite and its sub-properties, and on cito:isCitedBy.

Domain restrictions removed on cito:globalCitationFrequency and cito:inTextCitationFrequency.

Range restriction removed on cito:inTextCitationTarget.

20 New Subclasses of CiTO:Work


cito:AuthorityFile                                   (Subclass of cito:Specification)

cito:BibliographicMetadata                         (Subclass of cito:Metadata)



cito:CitationMetadata                                         (Subclass of cito:Metadata)

cito:ClinicalCaseReport                                      (Subclass of cito:Report)

cito:ClinicalTrialDesign                                      (Subclass of cito:Specification)

cito:ClinicalTrialReport                                      (Subclass of cito:Report)

cito:EntityMetadata                              (Subclass of cito:Metadata)


cito: Metadata

cito:MinimalInformationStandard                     (Subclass of cito:Specification)


cito:ProjectMetadata                                            (Subclass of cito:Metadata)

cito:ReportingStandard                      (Subclass of cito:Specification)

cito:StandardOperatingProcedure                    (Subclass of cito:Specification)

cito:TechnicalStandard                                   (Subclass of cito:Specification)

cito:Thesis                                                    (Originally mis-classified as a Subclass of cito:Expression)

cito:Workflow                                         (Subclass of cito:Specification)

3 Renamed Subclasses of CiTO:Work

cito:Catalog                                           (Formerly cito:Catalogue)

cito:ExperimentalProtocol                                  (Formerly cito:Protocol)

cito:Proposition                                     (Formerly cito:Explanation)    

5 Deprecated Subclass of CiTO:Work

cito:Discussion                                        (Deleted)

cito:Editorial                                                          (Originally mis-classified, now placed as a Subclass of cito:Expression)

cito:Message                                            (Deleted)

cito:Software                                                          (Originally mis-classified, now placed as a Subclass of cito:Expression)

cito:ScholarlyText                                  (Deleted)

 26 New Subclasses of CiTO:Expression

cito:Abstract                                           (Subclass of cito:Document)

 cito:CaseForSupportDocument                         (Subclass of cito:Document)

 cito:ConferenceProceedings                              (Subclass of cito:Document) 


cito:Editorial                                          (Previously mis-classified as a subclass of cito:Work)

cito:GrantApplicationDocument                        (Subclass of cito:Document)

cito:Journal                                             (Subclass of cito:Periodical)

cito:JournalIssue                                       (Subclass of cito:PeriodicalIssue)      

cito:Letter                                                (Subclass of cito:Document)

cito:Magazine                                         (Subclass of cito:Periodical)

cito:MagazineArticle                             (Subclass of cito:PeriodicalItem)

cito:MagazineIssue                                 (Subclass of cito:PeriodicalIssue)

cito:Manuscript                                      (Subclass of cito:Document)

cito:Newspaper                                       (Subclass of cito:Periodical)

cito:NewspaperArticle                           (Subclass of cito:PeriodicalItem)

cito:NewspaperIssue                              (Subclass of cito:PeriodicalIssue)

cito:PatentApplicationDocument                      (Subclass of cito:Document.)


cito:PeriodicalIssue                               (Subclass of cito:Document)

cito:PeriodicalItem                                (Subclass of cito:Document)


cito:PressRelease                                    (Subclass of cito:Document)

cito:Software                                           (Previously mis-classified as a Subclass of cito:Work)

cito:SupplementaryInformation                          (Subclasses of cito:Document)


cito:WikiEntry                                         (Subclass of cito:WebContent)

1 Renamed Subclass of CiTO:Expression

cito:BlogEntry                                        (Formerly cito:Blog) (Subclass of cito:WebContent)

2 Deprecated Subclass of CiTO:Expression

cito:TextFile                                                    (Deleted)

cito:Thesis                                               (Previously mis-classified, now placed as a Subclass of cito:Work)

1 New Subclasses of CiTO:Manifestation


3 Renamed Subclasses of CiTO:Manifestation

cito:DigitalMediaFile                                (Subclass of cito:ComputerFile)  (Formerly cito:DigitalMediaObject)

cito:OnlineFile                                         (Subclass of cito:ComputerFile)  (Formerly cito:OnlineDocument)

cito:PrintObject                                                     (Formerly cito:PrintDocument)


Throughout the ontology, several class and property definitions were altered to clarify their meaning, without changing their sense.


Summary of changes between published CiTO versions


CiTO v1.3

CiTO v1.4

CiTO v1.5

CiTO v1.6

Object properties





Data properties










Sub-classes of cito:Work





Sub-classes of cito:Expression





Sub-classes of cito:Manifestation







The contributions to this work of Katie Portwin, who participated in the development of the initial CiTO prototype, and of Alistair Miles and Graham Klyne, for helpful discussions on ontology structure, guidance in RDF modelling and syntax, and help in ontology coding and publication, are gratefully acknowledged. 

The development of CiTO forms part of the work of the Ontogenesis Network, a network of excellence to foster the creation, ontogeny and evolution of biological, bioinformatics and medical ontologies, supported by EPSRC grant EP/E021352/1.