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<!DOCTYPE html> <html class="client-nojs" lang="en" dir="ltr"> <head> <meta charset="UTF-8"> <title>Wikidata:WikiProject Ontology/Classes - Wikidata</title> <script>(function(){var className="client-js";var cookie=document.cookie.match(/(?:^|; )wikidatawikimwclientpreferences=([^;]+)/);if(cookie){cookie[1].split('%2C').forEach(function(pref){className=className.replace(new RegExp('(^| )'+pref.replace(/-clientpref-\w+$|[^\w-]+/g,'')+'-clientpref-\\w+( |$)'),'$1'+pref+'$2');});}document.documentElement.className=className;}());RLCONF={"wgBreakFrames":false,"wgSeparatorTransformTable":["",""],"wgDigitTransformTable":["",""],"wgDefaultDateFormat":"dmy","wgMonthNames":["","January","February","March","April","May","June","July","August","September","October","November","December"],"wgRequestId":"e38a77f4-250d-435c-a951-f5f91557d02a","wgCanonicalNamespace":"Project","wgCanonicalSpecialPageName":false,"wgNamespaceNumber":4,"wgPageName":"Wikidata:WikiProject_Ontology/Classes","wgTitle":"WikiProject Ontology/Classes","wgCurRevisionId":1671554970,"wgRevisionId":1671554970,"wgArticleId":23280832,"wgIsArticle":true,"wgIsRedirect":false,"wgAction":"view", "wgUserName":null,"wgUserGroups":["*"],"wgCategories":[],"wgPageViewLanguage":"en","wgPageContentLanguage":"en","wgPageContentModel":"wikitext","wgRelevantPageName":"Wikidata:WikiProject_Ontology/Classes","wgRelevantArticleId":23280832,"wgIsProbablyEditable":true,"wgRelevantPageIsProbablyEditable":true,"wgRestrictionEdit":[],"wgRestrictionMove":[],"wgNoticeProject":"wikidata","wgCiteReferencePreviewsActive":true,"wgMediaViewerOnClick":true,"wgMediaViewerEnabledByDefault":true,"wgVisualEditor":{"pageLanguageCode":"en","pageLanguageDir":"ltr","pageVariantFallbacks":"en"},"wgMFDisplayWikibaseDescriptions":{"search":true,"watchlist":true,"tagline":false,"nearby":true},"wgWMESchemaEditAttemptStepOversample":false,"wgWMEPageLength":5000,"wgCentralAuthMobileDomain":false,"wgEditSubmitButtonLabelPublish":true,"wgDiscussionToolsFeaturesEnabled":{"replytool":true,"newtopictool":true,"sourcemodetoolbar":true,"topicsubscription":false,"autotopicsub":false,"visualenhancements":false, "visualenhancements_reply":false,"visualenhancements_pageframe":false},"wgDiscussionToolsFallbackEditMode":"source","wgULSPosition":"personal","wgULSisCompactLinksEnabled":true,"wgVector2022LanguageInHeader":false,"wgULSisLanguageSelectorEmpty":false,"wgCheckUserClientHintsHeadersJsApi":["brands","architecture","bitness","fullVersionList","mobile","model","platform","platformVersion"]};RLSTATE={"ext.globalCssJs.user.styles":"ready","site.styles":"ready","user.styles":"ready","ext.globalCssJs.user":"ready","user":"ready","user.options":"loading","ext.discussionTools.init.styles":"ready","oojs-ui-core.styles":"ready","oojs-ui.styles.indicators":"ready","mediawiki.widgets.styles":"ready","oojs-ui-core.icons":"ready","skins.vector.styles.legacy":"ready","ext.visualEditor.desktopArticleTarget.noscript":"ready","codex-search-styles":"ready","ext.uls.pt":"ready","wikibase.client.init":"ready","ext.wikimediaBadges":"ready"};RLPAGEMODULES=["site","mediawiki.page.ready","mediawiki.toc", "skins.vector.legacy.js","wikibase.ui.entitysearch","ext.centralNotice.geoIP","ext.centralNotice.startUp","ext.gadget.Search","ext.gadget.ProtectionIndicators","ext.gadget.imagelinks","ext.gadget.NewSection","ext.gadget.formWizard","ext.urlShortener.toolbar","ext.centralauth.centralautologin","ext.visualEditor.desktopArticleTarget.init","ext.visualEditor.targetLoader","ext.echo.centralauth","ext.discussionTools.init","ext.eventLogging","ext.wikimediaEvents","ext.wikimediaEvents.wikibase","ext.navigationTiming","ext.uls.compactlinks","ext.uls.interface","ext.checkUser.clientHints"];</script> <script>(RLQ=window.RLQ||[]).push(function(){mw.loader.impl(function(){return["user.options@12s5i",function($,jQuery,require,module){mw.user.tokens.set({"patrolToken":"+\\","watchToken":"+\\","csrfToken":"+\\"}); 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We will define a <b>class-item</b> is any <a href="/wiki/Help:Items" title="Help:Items">item</a> used as value in a <a href="/wiki/Property:P31" title="Property:P31">instance of <small dir="ltr">(P31)</small></a> statement or with a <a href="/wiki/Property:P279" title="Property:P279">subclass of <small dir="ltr">(P279)</small></a> statement (subclass) or used as value in a <a href="/wiki/Property:P279" title="Property:P279">subclass of <small dir="ltr">(P279)</small></a> statement (superclass). Class-items are mostly used together with <b>instance-items</b>. By definition an instance-item in Wikidata is any item with a <a href="/wiki/Property:P31" title="Property:P31">instance of <small dir="ltr">(P31)</small></a> statement. </p><p><br/> For more information about classes and instances in Wikidata see: </p> <ul><li><a href="/wiki/Property:P279" title="Property:P279">subclass of <small dir="ltr">(P279)</small></a> and its discussion page</li> <li><a href="/wiki/Help:Basic_membership_properties" title="Help:Basic membership properties">Help:Basic membership properties</a></li> <li><a href="/wiki/Wikidata:Item_classification" title="Wikidata:Item classification">Wikidata:Item classification</a></li> <li><a href="/wiki/User:TomT0m/Classification" title="User:TomT0m/Classification">User:TomT0m/Classification</a></li> <li>...</li></ul> <p><i>this information should be consolidated and merged into one page</i> </p> <div id="toc" class="toc" role="navigation" aria-labelledby="mw-toc-heading"><input type="checkbox" role="button" id="toctogglecheckbox" class="toctogglecheckbox" style="display:none" /><div class="toctitle" lang="en" dir="ltr"><h2 id="mw-toc-heading">Contents</h2><span class="toctogglespan"><label class="toctogglelabel" for="toctogglecheckbox"></label></span></div> <ul> <li class="toclevel-1 tocsection-1"><a href="#Aspects_of_classes_in_ontologies"><span class="tocnumber">1</span> <span class="toctext">Aspects of classes in ontologies</span></a> <ul> <li class="toclevel-2 tocsection-2"><a href="#Definition"><span class="tocnumber">1.1</span> <span class="toctext">Definition</span></a></li> <li class="toclevel-2 tocsection-3"><a href="#Subsumption"><span class="tocnumber">1.2</span> <span class="toctext">Subsumption</span></a> <ul> <li class="toclevel-3 tocsection-4"><a href="#Transitivity_of_Subsumption"><span class="tocnumber">1.2.1</span> <span class="toctext">Transitivity of Subsumption</span></a></li> <li class="toclevel-3 tocsection-5"><a href="#Subsumption_Cycles"><span class="tocnumber">1.2.2</span> <span class="toctext">Subsumption Cycles</span></a></li> </ul> </li> <li class="toclevel-2 tocsection-6"><a href="#Extensional_vs._Intensional"><span class="tocnumber">1.3</span> <span class="toctext">Extensional vs. Intensional</span></a></li> <li class="toclevel-2 tocsection-7"><a href="#Disjointness_of_Classes"><span class="tocnumber">1.4</span> <span class="toctext">Disjointness of Classes</span></a></li> </ul> </li> <li class="toclevel-1 tocsection-8"><a href="#Class_restrictions"><span class="tocnumber">2</span> <span class="toctext">Class restrictions</span></a> <ul> <li class="toclevel-2 tocsection-9"><a href="#Quantifier_restrictions"><span class="tocnumber">2.1</span> <span class="toctext">Quantifier restrictions</span></a></li> <li class="toclevel-2 tocsection-10"><a href="#Cardinality_restrictions"><span class="tocnumber">2.2</span> <span class="toctext">Cardinality restrictions</span></a></li> </ul> </li> <li class="toclevel-1 tocsection-11"><a href="#Class_in_Wikidata"><span class="tocnumber">3</span> <span class="toctext">Class in Wikidata</span></a> <ul> <li class="toclevel-2 tocsection-12"><a href="#Class_naming"><span class="tocnumber">3.1</span> <span class="toctext">Class naming</span></a></li> </ul> </li> <li class="toclevel-1 tocsection-13"><a href="#References"><span class="tocnumber">4</span> <span class="toctext">References</span></a></li> </ul> </div> <div class="mw-heading mw-heading2 ext-discussiontools-init-section"><h2 id="Aspects_of_classes_in_ontologies" data-mw-thread-id="h-Aspects_of_classes_in_ontologies"><span data-mw-comment-start="" id="h-Aspects_of_classes_in_ontologies"></span>Aspects of classes in ontologies<span data-mw-comment-end="h-Aspects_of_classes_in_ontologies"></span></h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wikidata:WikiProject_Ontology/Classes&action=edit&section=1" title="Edit section: Aspects of classes in ontologies"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Definition" data-mw-thread-id="h-Definition-Aspects_of_classes_in_ontologies"><span data-mw-comment-start="" id="h-Definition-Aspects_of_classes_in_ontologies"></span>Definition<span data-mw-comment-end="h-Definition-Aspects_of_classes_in_ontologies"></span></h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wikidata:WikiProject_Ontology/Classes&action=edit&section=2" title="Edit section: Definition"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>There are multiple aspects of classes in ontologies. Please refer to the corresponding Wikipedia articles for definition of class and related terms. </p> <ul><li><a href="/wiki/Q5127848" title="Q5127848">class <small>(Q5127848)</small></a>: <small><span lang="">group of things derived from extensional or intensional definition (philosophy)</span></small></li> <li><a href="/wiki/Q16889133" title="Q16889133">class <small>(Q16889133)</small></a>: <small><span lang="">collection of items defined by common characteristics</span></small></li> <li><a href="/wiki/Q217594" title="Q217594">class <small>(Q217594)</small></a>: <small><span lang="">mathematical collection of sets that can be defined based on a property of its members (set theory)</span></small></li></ul> <div class="mw-heading mw-heading3"><h3 id="Subsumption" data-mw-thread-id="h-Subsumption-Aspects_of_classes_in_ontologies"><span data-mw-comment-start="" id="h-Subsumption-Aspects_of_classes_in_ontologies"></span>Subsumption<span data-mw-comment-end="h-Subsumption-Aspects_of_classes_in_ontologies"></span></h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wikidata:WikiProject_Ontology/Classes&action=edit&section=3" title="Edit section: Subsumption"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A class is more general than another when every item that belongs to the second also belongs to the first, as in <a href="/wiki/Q729" title="Q729">animal <small>(Q729)</small></a> is more general than <a href="/wiki/Q144" title="Q144">dog <small>(Q144)</small></a>. The more-general class is said to subsume the more-specific class. A class subsumed by another is called a subclass (or subtype) of the subsuming class (or supertype). </p><p>Because all items belonging to the subclass also belong to the superclass, any commonality of items belonging to the superclass is also a commonality of objects belonging to the subclass. This relationship is often called inheritance. </p><p>A class can be the direct subclass of several classes, permitting multiple inheritance. </p> <div class="mw-heading mw-heading4"><h4 id="Transitivity_of_Subsumption" data-mw-thread-id="h-Transitivity_of_Subsumption-Subsumption"><span data-mw-comment-start="" id="h-Transitivity_of_Subsumption-Subsumption"></span>Transitivity of Subsumption<span data-mw-comment-end="h-Transitivity_of_Subsumption-Subsumption"></span></h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wikidata:WikiProject_Ontology/Classes&action=edit&section=4" title="Edit section: Transitivity of Subsumption"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Because of the definition of subclass, if B is a subclass of A and C is a subclass of B then C is a subclass of A. </p> <div class="mw-heading mw-heading4"><h4 id="Subsumption_Cycles" data-mw-thread-id="h-Subsumption_Cycles-Subsumption"><span data-mw-comment-start="" id="h-Subsumption_Cycles-Subsumption"></span>Subsumption Cycles<span data-mw-comment-end="h-Subsumption_Cycles-Subsumption"></span></h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wikidata:WikiProject_Ontology/Classes&action=edit&section=5" title="Edit section: Subsumption Cycles"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A cycle is created if class A has a subclass B and B is a superclass of A. </p> <div class="mw-heading mw-heading3"><h3 id="Extensional_vs._Intensional" data-mw-thread-id="h-Extensional_vs._Intensional-Aspects_of_classes_in_ontologies"><span data-mw-comment-start="" id="h-Extensional_vs._Intensional-Aspects_of_classes_in_ontologies"></span>Extensional vs. Intensional<span data-mw-comment-end="h-Extensional_vs._Intensional-Aspects_of_classes_in_ontologies"></span></h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wikidata:WikiProject_Ontology/Classes&action=edit&section=6" title="Edit section: Extensional vs. Intensional"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Most classes in ontologies have an intentional aspect, i.e., there is an implicit or explicit definition of which items belong to the class. For example, <a href="/wiki/Q5" title="Q5">human <small>(Q5)</small></a> is the class of humans. An item belongs to this class if and only if it is a member of the species homo sapiens. This is independent of whether all such items are explicitly stated to belong to the class or whether there is a formal definition in the ontology of the membership requirements. </p><p>A few classes in ontologies may be strictly extensional, i.e., items belong to the class solely by being listed as a member of it. </p> <div class="mw-heading mw-heading3"><h3 id="Disjointness_of_Classes" data-mw-thread-id="h-Disjointness_of_Classes-Aspects_of_classes_in_ontologies"><span data-mw-comment-start="" id="h-Disjointness_of_Classes-Aspects_of_classes_in_ontologies"></span>Disjointness of Classes<span data-mw-comment-end="h-Disjointness_of_Classes-Aspects_of_classes_in_ontologies"></span></h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wikidata:WikiProject_Ontology/Classes&action=edit&section=7" title="Edit section: Disjointness of Classes"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Classes may be disjoint from one another, i.e., they cannot have any instances in common, as in <a href="/wiki/Q5" title="Q5">human <small>(Q5)</small></a> is disjoint from <a href="/wiki/Q144" title="Q144">dog <small>(Q144)</small></a>. Stating disjointness of classes in an ontology permits the flagging of questionable combinations of facts. For example, if disjointness of humans and dogs is stated in an ontology then items that belong to both classes could be flagged for investigation. </p><p>A collection of pairwise disjoint classes whose union has the same members as another class is said to be an exhaustive partition of that class. </p> <div class="mw-heading mw-heading2 ext-discussiontools-init-section"><h2 id="Class_restrictions" data-mw-thread-id="h-Class_restrictions"><span data-mw-comment-start="" id="h-Class_restrictions"></span>Class restrictions<span data-mw-comment-end="h-Class_restrictions"></span></h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wikidata:WikiProject_Ontology/Classes&action=edit&section=8" title="Edit section: Class restrictions"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Quantifier_restrictions" data-mw-thread-id="h-Quantifier_restrictions-Class_restrictions"><span data-mw-comment-start="" id="h-Quantifier_restrictions-Class_restrictions"></span>Quantifier restrictions<span data-mw-comment-end="h-Quantifier_restrictions-Class_restrictions"></span></h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wikidata:WikiProject_Ontology/Classes&action=edit&section=9" title="Edit section: Quantifier restrictions"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Quantifier restriction can be divided into two groups: </p> <ul><li>existential restriction: class with individuals having at least one property <i>p</i> with value <i>a</i></li> <li>universal restriction: class with individuals having only property <i>p</i> with value <i>a</i></li></ul> <div class="mw-heading mw-heading3"><h3 id="Cardinality_restrictions" data-mw-thread-id="h-Cardinality_restrictions-Class_restrictions"><span data-mw-comment-start="" id="h-Cardinality_restrictions-Class_restrictions"></span>Cardinality restrictions<span data-mw-comment-end="h-Cardinality_restrictions-Class_restrictions"></span></h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wikidata:WikiProject_Ontology/Classes&action=edit&section=10" title="Edit section: Cardinality restrictions"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li>minimal cardinality restriction: restriction defined by a minimal number of relations</li> <li>maximal cardinality restriction: restriction defined by a maximal number of relations</li> <li>qualified cardinality restriction: restriction defined by a fixed number of relations</li></ul> <div class="mw-heading mw-heading2 ext-discussiontools-init-section"><h2 id="Class_in_Wikidata" data-mw-thread-id="h-Class_in_Wikidata"><span data-mw-comment-start="" id="h-Class_in_Wikidata"></span>Class in Wikidata<span data-mw-comment-end="h-Class_in_Wikidata"></span></h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wikidata:WikiProject_Ontology/Classes&action=edit&section=11" title="Edit section: Class in Wikidata"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Class_naming" data-mw-thread-id="h-Class_naming-Class_in_Wikidata"><span data-mw-comment-start="" id="h-Class_naming-Class_in_Wikidata"></span>Class naming<span data-mw-comment-end="h-Class_naming-Class_in_Wikidata"></span></h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wikidata:WikiProject_Ontology/Classes&action=edit&section=12" title="Edit section: Class naming"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><b>Singular or plural?</b> </p><p>Wikidata labels for classes should be singular, at least in English. See also the guidelines in <a href="/wiki/Help:Label" title="Help:Label">Help:Label</a>. </p> <div class="mw-heading mw-heading2 ext-discussiontools-init-section"><h2 id="References" data-mw-thread-id="h-References"><span data-mw-comment-start="" id="h-References"></span>References<span data-mw-comment-end="h-References"></span></h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Wikidata:WikiProject_Ontology/Classes&action=edit&section=13" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a rel="nofollow" class="external text" href="http://protege.stanford.edu/publications/ontology_development/ontology101.pdf">Ontology Development 101: A Guide to Creating Your First Ontology</a>, Natalya F. Noy and Deborah L. McGuinness, 2001</li> <li><a rel="nofollow" class="external text" href="https://wiki.phenoscape.org/wiki/Ontologies#Taxonomy_Ontologies,">interesting structure for metaclass</a></li> <li><a rel="nofollow" class="external text" href="http://protege.stanford.edu/conference/2006/submissions/abstracts/7.2_Wang_Hai_Protege_conf.pdf">Two types of ontologies</a>, comparison of two types of ontologies with consequences on their class structure</li> <li><a rel="nofollow" class="external text" href="http://www.eecs.yorku.ca/course_archive/2009-10/W/3311/slides/19-Inheritance.pdf">visualization doc</a></li></ul>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" 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