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href="/wiki/Special:MyLanguage/User:TomT0m" title="Special:MyLanguage/User:TomT0m">User:TomT0m</a></bdi></div></div></div> <div id="contentSub2"></div> <div id="jump-to-nav"></div> <a class="mw-jump-link" href="#mw-head">Jump to navigation</a> <a class="mw-jump-link" href="#searchInput">Jump to search</a> <div id="mw-content-text" class="mw-body-content"><div class="mw-pt-translate-header noprint" dir="ltr" lang="en">This page is a <span class="plainlinks"><a class="external text" href="https://www.wikidata.org/w/index.php?title=Special:Translate&group=page-User%3ATomT0m%2FClassification&action=page&filter=&language=it">translated version</a></span> of the page <a href="/wiki/User:TomT0m/Classification" title="User:TomT0m/Classification">User:TomT0m/Classification</a> and the translation is 17% complete.</div><div class="mw-pt-translate-header" dir="ltr" lang="en"><span class="mw-translate-fuzzy">Outdated translations are marked like this.</span></div><div class="mw-content-ltr mw-parser-output" lang="it" dir="ltr"><div class="mw-pt-languages noprint navigation-not-searchable" lang="en" dir="ltr"><div class="mw-pt-languages-label">Other languages:</div><ul class="mw-pt-languages-list"><li><a href="/wiki/User:TomT0m/Classification/de" class="mw-pt-progress mw-pt-progress--med" title="User:TomT0m/Klassifikation (17% translated)" lang="de" dir="ltr">Deutsch</a></li> <li><a href="/wiki/User:TomT0m/Classification" class="mw-pt-languages-ui mw-pt-progress mw-pt-progress--complete" title="User:TomT0m/Classification (100% translated)" lang="en" dir="ltr">English</a></li> <li><a href="/wiki/User:TomT0m/Classification/nl" class="mw-pt-progress mw-pt-progress--low" title="Gebruiker:TomT0m/Klassificatie (2% translated)" lang="nl" dir="ltr">Nederlands</a></li> <li><a href="/wiki/User:TomT0m/Classification/fr" class="mw-pt-progress mw-pt-progress--med" title="Utilisateur:TomT0m/Classification (69% translated)" lang="fr" dir="ltr">français</a></li> <li><span class="mw-pt-languages-selected mw-pt-progress mw-pt-progress--med" lang="it" dir="ltr">italiano</span></li> <li><a href="/wiki/User:TomT0m/Classification/pt-br" class="mw-pt-progress mw-pt-progress--med" title="Utilisador:TomT0m/Classificação (18% translated)" lang="pt-BR" dir="ltr">português do Brasil</a></li> <li><a href="/wiki/User:TomT0m/Classification/ru" class="mw-pt-progress mw-pt-progress--low" title="Помощь:Классификация (12% translated)" lang="ru" dir="ltr">русский</a></li> <li><a href="/wiki/User:TomT0m/Classification/uk" class="mw-pt-progress mw-pt-progress--low" title="User:TomT0m/Класифікація (8% translated)" lang="uk" dir="ltr">українська</a></li></ul></div> <table class="draft layouttemplate" style="border: 1px solid #a2a9b1; width: 80%; margin: 0 auto 1em; padding: .2em; max-width: 65em; background: AntiqueWhite;"> <tbody><tr> <td style="width:50px"><span typeof="mw:File"><span><img src="//upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Gnome-preferences-system.svg/45px-Gnome-preferences-system.svg.png" decoding="async" width="45" height="45" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Gnome-preferences-system.svg/68px-Gnome-preferences-system.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Gnome-preferences-system.svg/90px-Gnome-preferences-system.svg.png 2x" data-file-width="48" data-file-height="48" /></span></span> </td> <td><div class="center"><div lang="en" dir="ltr" class="description en">This page is a <b>work in progress</b>, not an article or policy, and may be incomplete and/or unreliable.<br />Please offer suggestions on the <a href="/w/index.php?title=User_talk:TomT0m/Classification/it&action=edit&redlink=1" class="new" title="User talk:TomT0m/Classification/it (page does not exist)">talk page</a>.</div> <hr /><span style="font-size:x-small;line-height:140%" class="plainlinks"> <p><a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/bn">বাংলা</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/ca">català</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/cs">čeština</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/de">Deutsch</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/en">English</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/es">español</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/fa">فارسی</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/fi">suomi</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/fr">français</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/hi">हिन्दी</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/hu">magyar</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/it">italiano</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/ja">日本語</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/ja">한국어</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/lb">Lëtzebuergesch</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/lv">latviešu</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/mk">македонски</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/ms">Bahasa Melayu</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/my">မြန်မာဘာသာ</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/nb">norsk bokmål</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/nl">Nederlands</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/pa">ਪੰਜਾਬੀ</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/pl">polski</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/pnb">پنجابی</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/pt">português</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/pt-br">português do Brasil</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/ro">română</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/sco">Scots</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/sq">shqip</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/sl">slovenščina</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/sr">српски / srpski</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/sv">svenska</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/tr">Türkçe</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/ru">русский</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/uk">українська</a> | <a class="external text" href="https://www.wikidata.org/wiki/Template:Draft/zh-hans">中文（简体）</a> | <small class="plainlinks" title="Edit Template:Draft/lang"><a class="external text" href="https://www.wikidata.org/w/index.php?title=Template:Draft/lang&action=edit">+/−</a></small> </p> </span></div> </td></tr></tbody></table> <p>La <i>classificazione</i>, o <a href="/wiki/Q7211" title="Q7211">taxonomy <small>(Q7211)</small></a>, è l'arte di raggruppare e riordinare oggetti o concetti che hanno caratteristiche comuni e discriminarli se non le hanno. Il contenuto delle voci <a href="https://en.wikipedia.org/wiki/Classification" class="extiw" title="en:Classification">Classificazione</a> o <a href="https://en.wikipedia.org/wiki/Taxonomy" class="extiw" title="en:Taxonomy">Tassonomia</a> della Wikipedia in lingua Inglese dimostrano che essi sono argomenti assai studiati e che ogni branca della conoscenza umana è stata nel tempo soggetta a un qualche tentativo (spesso numerosi) di classificazione. </p><p>La classificazione adoperata in Wikidata si basa su tecniche ben note ispirate dalle cosiddette <i>tecnologie semantiche</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="#Classi_e_istanze"><span class="tocnumber">1</span> <span class="toctext">Classi e istanze</span></a> <ul> <li class="toclevel-2 tocsection-2"><a href="#Class-token_distinction"><span class="tocnumber">1.1</span> <span class="toctext">Class-token distinction</span></a></li> <li class="toclevel-2 tocsection-3"><a href="#Superclasses_and_subclasses:_relationships_between_classes"><span class="tocnumber">1.2</span> <span class="toctext">Superclasses and subclasses: relationships between classes</span></a></li> <li class="toclevel-2 tocsection-4"><a href="#Classes_definition"><span class="tocnumber">1.3</span> <span class="toctext">Classes definition</span></a></li> </ul> </li> <li class="toclevel-1 tocsection-5"><a href="#Classifying_classes"><span class="tocnumber">2</span> <span class="toctext">Classifying classes</span></a> <ul> <li class="toclevel-2 tocsection-6"><a href="#Why_having_items_which_are_both_class_and_instances"><span class="tocnumber">2.1</span> <span class="toctext">Why having items which are both class and instances</span></a></li> <li class="toclevel-2 tocsection-7"><a href="#Class_of_instances,_class_of_class_of_instances,_..."><span class="tocnumber">2.2</span> <span class="toctext">Class of instances, class of class of instances, ...</span></a></li> </ul> </li> <li class="toclevel-1 tocsection-8"><a href="#Tools_and_properties"><span class="tocnumber">3</span> <span class="toctext">Tools and properties</span></a> <ul> <li class="toclevel-2 tocsection-9"><a href="#Properties_associated_to_a_class"><span class="tocnumber">3.1</span> <span class="toctext">Properties associated to a class</span></a></li> </ul> </li> <li class="toclevel-1 tocsection-10"><a href="#Related"><span class="tocnumber">4</span> <span class="toctext">Related</span></a></li> <li class="toclevel-1 tocsection-11"><a href="#Notes"><span class="tocnumber">5</span> <span class="toctext">Notes</span></a></li> </ul> </div> <div class="mw-heading mw-heading2"><h2 id="Classi_e_istanze">Classi e istanze</h2></div> <p>Io, autore, e tu, lettore, così come chiunque legga questa pagina, abbiamo qualcosa in comune. Tutti apparteniamo al gruppo di persone che lavora o che vuole lavorare a Wikidata. Chiamiamo questo gruppo "Wikidatiani". </p><p>Naturalmente esistono altri esempi di gruppi nel mondo reale, come ad esempio </p> <ul><li>il gruppo di tutte le persone che hanno mai contribuito a qualsiasi altro progetto della Wikimedia Foundation</li> <li>il gruppo di tutti gli alberi del mondo</li></ul> <p>Esistono un mucchio di gruppi, di tutti i tipi, su Wikidata. Quelli a cui noi siamo interessati sono chiamati <i>classi</i>. Altri tipi di classi, come ad esempio i complessi musicali, non sono ciò di cui parla quest'articolo. Gli elementi delle classi sono chiamati "<i>istanze</i>" o <i>individui</i>. Gli elementi di una classe sono determinati dalla proprietà che definisce la classe. </p><p>La proprietà che lega un individuo, come te e me, alla classe o alle classi a cui esso appartiene: <a href="/wiki/Property:P31" title="Property:P31">instance of <small dir="ltr">(P31)</small></a> Per esempio, se si vuol dire che Barack Obama è un essere umano, ciò si traduce nel linguaggio di Wikidata in questa maniera: </p> <div class="mw-translate-fuzzy"> <ul><li><div style="border: 1px solid #C9C9C9;background-color: #F9F9F9;vertical-align:top;display: inline-block;"><span style="background:None;">⟨ <span style="font-family:fixed;"><a href="/wiki/Q76" title="Q76">Barack Obama <small>(Q76)</small></a><span class="external_link-reasonator">  <span typeof="mw:File"><a href="https://reasonator.toolforge.org/?q=Q76&lang=en" title="View with Reasonator"><img alt="View with Reasonator" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/12px-Wikidata-Reasonator_small_logo.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/18px-Wikidata-Reasonator_small_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/24px-Wikidata-Reasonator_small_logo.svg.png 2x" data-file-width="500" data-file-height="500" /></a></span></span><span class="external_link-SQID"> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=Q76&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></span></span> ⟩</span> <i><a href="/wiki/Property:P31" title="Property:P31">instance of <small dir="ltr">(P31)</small></a><small> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=P31&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></small></i> <span style="background:None;">⟨ <span style="font-family:fixed;"><a href="/wiki/Q5" title="Q5">human <small>(Q5)</small></a><span class="external_link-reasonator">  <span typeof="mw:File"><a href="https://reasonator.toolforge.org/?q=Q5&lang=en" title="View with Reasonator"><img alt="View with Reasonator" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/12px-Wikidata-Reasonator_small_logo.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/18px-Wikidata-Reasonator_small_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/24px-Wikidata-Reasonator_small_logo.svg.png 2x" data-file-width="500" data-file-height="500" /></a></span></span><span class="external_link-SQID"> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=Q5&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></span></span> ⟩</span></div>, <br /></li></ul> <p>in cui <a href="/wiki/Q5" title="Q5">human <small>(Q5)</small></a><span class="external_link-reasonator">  <span typeof="mw:File"><a href="https://reasonator.toolforge.org/?q=Q5&lang=en" title="View with Reasonator"><img alt="View with Reasonator" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/12px-Wikidata-Reasonator_small_logo.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/18px-Wikidata-Reasonator_small_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/24px-Wikidata-Reasonator_small_logo.svg.png 2x" data-file-width="500" data-file-height="500" /></a></span></span><span class="external_link-SQID"> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=Q5&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></span> corrisponde alla classe di tutti gli esseri umani e <a href="/wiki/Q76" title="Q76">Barack Obama <small>(Q76)</small></a><span class="external_link-reasonator">  <span typeof="mw:File"><a href="https://reasonator.toolforge.org/?q=Q76&lang=en" title="View with Reasonator"><img alt="View with Reasonator" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/12px-Wikidata-Reasonator_small_logo.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/18px-Wikidata-Reasonator_small_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/24px-Wikidata-Reasonator_small_logo.svg.png 2x" data-file-width="500" data-file-height="500" /></a></span></span><span class="external_link-SQID"> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=Q76&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></span> corrisponde all'elemento associato a Barack Obama. </p> </div> <dl><dt>A note about the <i>Wikidatian</i> example</dt> <dd></dd> <dd>There is a subtlety about the <i>Wikidatian</i> example. It can be argued that being a wikidata editor is better modeled as an occupation ( <a href="/wiki/Q12737077" title="Q12737077">occupation <small>(Q12737077)</small></a><span class="external_link-reasonator">  <span typeof="mw:File"><a href="https://reasonator.toolforge.org/?q=Q12737077&lang=en" title="View with Reasonator"><img alt="View with Reasonator" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/12px-Wikidata-Reasonator_small_logo.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/18px-Wikidata-Reasonator_small_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/24px-Wikidata-Reasonator_small_logo.svg.png 2x" data-file-width="500" data-file-height="500" /></a></span></span><span class="external_link-SQID"> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=Q12737077&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></span> - that is, a class of actions that are often performed by someone or something, or a rôle in society) than as a class of people. If that's the case, then the definition of the occupation would be <i>editing regularly Wikidata</i>. In this case, the property <a href="/wiki/Property:P106" title="Property:P106">occupation <small dir="ltr">(P106)</small></a><small> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=P106&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></small> is better suited, and the class of all people who have this occupation is distinct, although some wikidatians prefer not to make it explicit.</dd></dl> <div class="mw-heading mw-heading3"><h3 id="Class-token_distinction">Class-token distinction</h3></div> <p>An important thing to bear in mind when we want to decide whether or not an item is a member of a class is, to a first approximation, the philosophical principle of the Type/Token distinction, which itself has got an item on Wikidata: <a href="/wiki/Q175928" title="Q175928">type–token distinction <small>(Q175928)</small></a>. According to this principle, tokens (or <i>instances</i>, or <i>individuals</i>), are concrete objects, or events involving concrete objects, which are localized in time and space. </p><p>You and I are concrete objects, the <a href="/wiki/Q19024" title="Q19024">Boston Tea Party <small>(Q19024)</small></a> or the <a href="/wiki/Q323" title="Q323">Big Bang <small>(Q323)</small></a> is an <a href="/wiki/Q1190554" title="Q1190554">occurrence <small>(Q1190554)</small></a>: all of these are tokens. <i>The last time Napoleon got angry</i> is a token, it's an event involving someone. </p><p>Classes, on the other hand, are abstract objects that regroup tokens according to some common characteristic they have, for example, the class of all trees. Some concepts like the concept of "angryness" seems to be even more abstract. It's not the case. We showed a token of angryness in our last example: <i>The last time Napoleon got angry</i>. Grouped together with similar events they form a class we can assimilate to the concept of this state of mind. </p><p>To facilitate <a href="/wiki/Q1644136" title="Q1644136">higher-order logic <small>(Q1644136)</small></a> capabilities, some modern ontologies go further and allow classes to be instances of other classes, effectively providing more than a single layer of abstraction. See <a href="#Classifying_classes">below</a> for the discussion of this approach. </p> <div class="mw-heading mw-heading3"><h3 id="Superclasses_and_subclasses:_relationships_between_classes">Superclasses and subclasses: relationships between classes</h3></div> <p>In the following, the domain of discourse we are interested in is the Wikimedia project, and especially its contributors. The classes <i>Wikidatian</i> and <i>Wikimedian</i> are classes relevant in this context. Clearly every person who is a member of <i>Wikidatian</i> has contributed to a Wikimedia project. There is a property in Wikidata to express this kind of relationship: <a href="/wiki/Property:P279" title="Property:P279">subclass of <small dir="ltr">(P279)</small></a>. For example a claim like </p> <dl><dd><div style="border: 1px solid #C9C9C9;background-color: #F9F9F9;vertical-align:top;display: inline-block;"><span style="background:None;">⟨ <span style="font-family:fixed;">Wikidatians</span> ⟩</span> <i><a href="/wiki/Property:P279" title="Property:P279">subclass of <small dir="ltr">(P279)</small></a><small> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=P279&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></small></i> <span style="background:None;">⟨ <span style="font-family:fixed;">Wikimedians</span> ⟩</span></div></dd></dl> <p>means that every instance of the former class is also an instance of the latter. </p><p>Similarly, it is very likely that Wikimedians are all human. This would translate in the common language we are defining, independent of the respective languages of Wikidata contributors. </p> <ul><li><div style="border: 1px solid #C9C9C9;background-color: #F9F9F9;vertical-align:top;display: inline-block;"><span style="background:None;">⟨ <span style="font-family:fixed;">Wikimedian</span> ⟩</span> <i><a href="/wiki/Property:P279" title="Property:P279">subclass of <small dir="ltr">(P279)</small></a><small> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=P279&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></small></i> <span style="background:None;">⟨ <span style="font-family:fixed;">Human</span> ⟩</span></div><sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>{{int joke}} 1<span class="cite-bracket">]</span></a></sup>.</li></ul> <p>There are other ways to translate the first statement in common language: </p> <ul><li><i>Wikidatian</i> is a special kind of <i>Wikimedian</i>; or, for those who are in computing or programming, the <i>Wikidatian</i> class is a specialisation of <i>Wikimedian</i> class.</li></ul> <p>The second statement is also sometimes written (if you hear this somewhere in a discussion, don't panic): </p> <ul><li>the <i>Human</i> class is a Generalization of the <i>Wikimedian</i> class ; all Wikimedians are human ; all instances of Wikimedian are instances of human.</li></ul> <p>A Wikimedian can be both a Wikipedian (the class of all people who contributed to Wikipedia) and a Wikidatian. This is not a problem. </p> <div class="mw-heading mw-heading3"><h3 id="Classes_definition">Classes definition</h3></div> <p>Imagine two Wikimedians, Bob and Alice. Imagine we have a database of all Wikimedians, and that we have information about them. In that database, we have also items about Wikimedia projects, like <i>Wikidata</i>, <i>Wikipedia</i>, <i>Wikisource</i>, ... </p><p>We also have a property called <i>contributes to</i>, with information such that: </p> <dl><dt>Alice</dt> <dd> <ul><li><div style="border: 1px solid #C9C9C9;background-color: #F9F9F9;vertical-align:top;display: inline-block;"><span style="background:None;">⟨ <span style="font-family:fixed;">Alice</span> ⟩</span> <i><i>contributes to</i> <small><a href="/wiki/Special:Search/Property:contributes_to" title="Special:Search/Property:contributes to">Search</a></small></i> <span style="background:None;">⟨ <span style="font-family:fixed;">Wikipedia</span> ⟩</span></div></li></ul></dd></dl> <dl><dt>Bob</dt> <dd> <ul><li><div style="border: 1px solid #C9C9C9;background-color: #F9F9F9;vertical-align:top;display: inline-block;"><span style="background:None;">⟨ <span style="font-family:fixed;">Bob</span> ⟩</span> <i><i>contributes to</i> <small><a href="/wiki/Special:Search/Property:contributes_to" title="Special:Search/Property:contributes to">Search</a></small></i> <span style="background:None;">⟨ <span style="font-family:fixed;">Wikisource</span> ⟩</span></div></li> <li><div style="border: 1px solid #C9C9C9;background-color: #F9F9F9;vertical-align:top;display: inline-block;"><span style="background:None;">⟨ <span style="font-family:fixed;">Bob</span> ⟩</span> <i><i>contributes to</i> <small><a href="/wiki/Special:Search/Property:contributes_to" title="Special:Search/Property:contributes to">Search</a></small></i> <span style="background:None;">⟨ <span style="font-family:fixed;">Wikidata</span> ⟩</span></div></li></ul></dd></dl> <p>We know from this data that Bob is a Wikidatian. In this case, we could use this property, hypothetically, to query the database for all Wikidatians. Actually this even could be used to give a precise definition of what the Wikidatian class is, using only things that are already present in the database. We could create what is called a <a href="/wiki/Q1026899" title="Q1026899">intensional definition <small>(Q1026899)</small></a><span class="external_link-reasonator">  <span typeof="mw:File"><a href="https://reasonator.toolforge.org/?q=Q1026899&lang=en" title="View with Reasonator"><img alt="View with Reasonator" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/12px-Wikidata-Reasonator_small_logo.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/18px-Wikidata-Reasonator_small_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/24px-Wikidata-Reasonator_small_logo.svg.png 2x" data-file-width="500" data-file-height="500" /></a></span></span><span class="external_link-SQID"> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=Q1026899&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></span> to the class. This is a thing people who are working on other projects do, and something to keep in mind to organize Wikidata: this could give definitions independent of the language of the contributor and a good definition of a class could be very useful for constraints and sanity checks, vandalism fighting, etc. ... All this based on the fact that, if we have a query that gives a good definition of a class, every instance of the class should be in the result set of the query. </p><p>Some tools can use class definition to deduce other things from existing statements and class definitions. For example, if we have statements about Alice and Bob that say they both contribute to Wikipedia (using the «contributes to» Property), and we know from the definition of the «Wikipedian» class that Wikipedians are people who contribute to Wikipedia, then a tool could deduce that Alice and Bob are Wikipedians, even if there are no explicit «instance of: Wikipedian» statements for their items. Then if Wikipedian is a subclass of Wikimedian, the tool could deduce that Alice and Bob are Wikimedian as well (if it's aware of the <a href="/wiki/Q64861" title="Q64861">transitive relation <small>(Q64861)</small></a><span class="external_link-reasonator">  <span typeof="mw:File"><a href="https://reasonator.toolforge.org/?q=Q64861&lang=en" title="View with Reasonator"><img alt="View with Reasonator" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/12px-Wikidata-Reasonator_small_logo.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/18px-Wikidata-Reasonator_small_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/24px-Wikidata-Reasonator_small_logo.svg.png 2x" data-file-width="500" data-file-height="500" /></a></span></span><span class="external_link-SQID"> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=Q64861&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></span> of the subclass relationship; that is, that an instance of a class is an instance of all its superclasses). </p><p>There is a project whose goal is to collect Wikidata's community needs and potential use cases in term of inferences (first) then to find ways to benefit them in Wikidata, please visit <a href="/wiki/Special:MyLanguage/Wikidata:WikiProject_Reasoning" title="Special:MyLanguage/Wikidata:WikiProject Reasoning">WikiProject Reasoning</a>. </p> <div class="mw-heading mw-heading2"><h2 id="Classifying_classes">Classifying classes</h2></div><p> It is sometimes useful to use some other classification methods and technologies that do not follow strictly the token/type relationship. For example there are already classifications in use for ships: </p><div style="border: 1px solid #C9C9C9;background-color: #F9F9F9;vertical-align:top;display: inline-block;"><span style="background:None;">⟨ <span style="font-family:fixed;"><a href="/wiki/Q5631188" title="Q5631188">HMS Aboukir <small>(Q5631188)</small></a><span class="external_link-reasonator">  <span typeof="mw:File"><a href="https://reasonator.toolforge.org/?q=Q5631188&lang=en" title="View with Reasonator"><img alt="View with Reasonator" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/12px-Wikidata-Reasonator_small_logo.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/18px-Wikidata-Reasonator_small_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/24px-Wikidata-Reasonator_small_logo.svg.png 2x" data-file-width="500" data-file-height="500" /></a></span></span><span class="external_link-SQID"> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=Q5631188&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></span></span> ⟩</span> <i><a href="/wiki/Property:P31" title="Property:P31">instance of <small dir="ltr">(P31)</small></a><small> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=P31&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></small></i> <span style="background:None;">⟨ <span style="font-family:fixed;"><a href="/wiki/Q4121227" title="Q4121227">Albion-class second-rate ship of the line <small>(Q4121227)</small></a><span class="external_link-reasonator">  <span typeof="mw:File"><a href="https://reasonator.toolforge.org/?q=Q4121227&lang=en" title="View with Reasonator"><img alt="View with Reasonator" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/12px-Wikidata-Reasonator_small_logo.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/18px-Wikidata-Reasonator_small_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/24px-Wikidata-Reasonator_small_logo.svg.png 2x" data-file-width="500" data-file-height="500" /></a></span></span><span class="external_link-SQID"> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=Q4121227&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></span></span> ⟩</span></div><p> is a natural things to say. The counterpart of this Wikidata statement exists in American Army members' language, who can say "<a href="/wiki/Q5631188" title="Q5631188">HMS Aboukir <small>(Q5631188)</small></a> is a ship of the class <a href="/wiki/Q4121227" title="Q4121227">Albion-class second-rate ship of the line <small>(Q4121227)</small></a>". So their language can easily have its counterpart in Wikidata. But how can we say that all ship classes on Wikidata are not necessarily ship classes in the sense used by the US-American Army? There are indeed a lot of types of ships (cruise ships, cargo ships) that would never be used in a sentence like "[...] is a ship of the class [...]" </p><p>The idea is that we can discriminate ship classes in the preceding sense from any ship class in the Wikidata sense by classifying classes themselves, using the same properties that we use to classify instances. </p><p>Actually Wikidata already had all that it needed to do that even before it existed: the item and the corresponding articles defined <a href="/wiki/Q559026" title="Q559026">ship class <small>(Q559026)</small></a> themselves. It can reasonably be said that </p> <dl><dd><div style="border: 1px solid #C9C9C9;background-color: #F9F9F9;vertical-align:top;display: inline-block;"><span style="background:None;">⟨ <span style="font-family:fixed;"><a href="/wiki/Q4121227" title="Q4121227">Albion-class second-rate ship of the line <small>(Q4121227)</small></a><span class="external_link-reasonator">  <span typeof="mw:File"><a href="https://reasonator.toolforge.org/?q=Q4121227&lang=en" title="View with Reasonator"><img alt="View with Reasonator" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/12px-Wikidata-Reasonator_small_logo.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/18px-Wikidata-Reasonator_small_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/24px-Wikidata-Reasonator_small_logo.svg.png 2x" data-file-width="500" data-file-height="500" /></a></span></span><span class="external_link-SQID"> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=Q4121227&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></span></span> ⟩</span> <i><a href="/wiki/Property:P279" title="Property:P279">subclass of <small dir="ltr">(P279)</small></a><small> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=P279&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></small></i> <span style="background:None;">⟨ <span style="font-family:fixed;"><a href="/wiki/Q11446" title="Q11446">ship <small>(Q11446)</small></a><span class="external_link-reasonator">  <span typeof="mw:File"><a href="https://reasonator.toolforge.org/?q=Q11446&lang=en" title="View with Reasonator"><img alt="View with Reasonator" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/12px-Wikidata-Reasonator_small_logo.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/18px-Wikidata-Reasonator_small_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/24px-Wikidata-Reasonator_small_logo.svg.png 2x" data-file-width="500" data-file-height="500" /></a></span></span><span class="external_link-SQID"> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=Q11446&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></span></span> ⟩</span></div>.</dd></dl> <p>But it can also reasonably be said that </p> <dl><dd><div style="border: 1px solid #C9C9C9;background-color: #F9F9F9;vertical-align:top;display: inline-block;"><span style="background:None;">⟨ <span style="font-family:fixed;"><a href="/wiki/Q4121227" title="Q4121227">Albion-class second-rate ship of the line <small>(Q4121227)</small></a><span class="external_link-reasonator">  <span typeof="mw:File"><a href="https://reasonator.toolforge.org/?q=Q4121227&lang=en" title="View with Reasonator"><img alt="View with Reasonator" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/12px-Wikidata-Reasonator_small_logo.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/18px-Wikidata-Reasonator_small_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/24px-Wikidata-Reasonator_small_logo.svg.png 2x" data-file-width="500" data-file-height="500" /></a></span></span><span class="external_link-SQID"> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=Q4121227&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></span></span> ⟩</span> <i><a href="/wiki/Property:P31" title="Property:P31">instance of <small dir="ltr">(P31)</small></a><small> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=P31&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></small></i> <span style="background:None;">⟨ <span style="font-family:fixed;"><a href="/wiki/Q559026" title="Q559026">ship class <small>(Q559026)</small></a><span class="external_link-reasonator">  <span typeof="mw:File"><a href="https://reasonator.toolforge.org/?q=Q559026&lang=en" title="View with Reasonator"><img alt="View with Reasonator" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/12px-Wikidata-Reasonator_small_logo.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/18px-Wikidata-Reasonator_small_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/24px-Wikidata-Reasonator_small_logo.svg.png 2x" data-file-width="500" data-file-height="500" /></a></span></span><span class="external_link-SQID"> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=Q559026&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></span></span> ⟩</span></div></dd></dl> <p>because it's clearly by itself an example of a ship class, and not only a subclass of ships. An army man would use that as an example of a ship class if he wanted to explain that concept to someone. </p> <dl><dd>In that case, <a href="/wiki/Q4121227" title="Q4121227">Albion-class second-rate ship of the line <small>(Q4121227)</small></a> is both a class and an instance: <ul><li>a class of ship, as it is a subclass of the <ship> concept</li> <li>an instance of the <ship class> concept.</li></ul></dd> <dd>This is allowed by semantic web standards like OWL Full or RDF. See the (currently only in english) <a href="/wiki/Q19478619" title="Q19478619">metaclass <small>(Q19478619)</small></a><span class="external_link-reasonator">  <span typeof="mw:File"><a href="https://reasonator.toolforge.org/?q=Q19478619&lang=en" title="View with Reasonator"><img alt="View with Reasonator" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/12px-Wikidata-Reasonator_small_logo.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/18px-Wikidata-Reasonator_small_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/24px-Wikidata-Reasonator_small_logo.svg.png 2x" data-file-width="500" data-file-height="500" /></a></span></span><span class="external_link-SQID"> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=Q19478619&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></span> english Wikipedia article.</dd></dl> <div class="mw-heading mw-heading3"><h3 id="Why_having_items_which_are_both_class_and_instances">Why having items which are both class and instances</h3></div> <p>Some people object that this feature, having items which are both classes and instances, is not useful. In their mind, it is enough to search for all the subclasses of some class to get all the relevant classes. We'll explain why it is not always enough. </p><p>Let's take the ship class example. Say we want to find all ship classes. Some sets of ship are things that are commonly called <i>ship class</i> (<a href="/wiki/Q559026" title="Q559026">ship class <small>(Q559026)</small></a><span class="external_link-reasonator">  <span typeof="mw:File"><a href="https://reasonator.toolforge.org/?q=Q559026&lang=en" title="View with Reasonator"><img alt="View with Reasonator" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/12px-Wikidata-Reasonator_small_logo.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/18px-Wikidata-Reasonator_small_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/24px-Wikidata-Reasonator_small_logo.svg.png 2x" data-file-width="500" data-file-height="500" /></a></span></span><span class="external_link-SQID"> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=Q559026&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></span>) in the real world. By definition <i>A <b>ship class</b> is a group of ships of a similar design</i>. <a href="/wiki/Q309336" title="Q309336">Nimitz-class aircraft carrier <small>(Q309336)</small></a><span class="external_link-reasonator">  <span typeof="mw:File"><a href="https://reasonator.toolforge.org/?q=Q309336&lang=en" title="View with Reasonator"><img alt="View with Reasonator" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/12px-Wikidata-Reasonator_small_logo.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/18px-Wikidata-Reasonator_small_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/24px-Wikidata-Reasonator_small_logo.svg.png 2x" data-file-width="500" data-file-height="500" /></a></span></span><span class="external_link-SQID"> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=Q309336&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></span> has a set of instances, 10 have been built. All are ships, so <a href="/wiki/Q309336" title="Q309336">Nimitz-class aircraft carrier <small>(Q309336)</small></a> is a subclass of <a href="/wiki/Q11446" title="Q11446">ship <small>(Q11446)</small></a>. <a href="/wiki/Q182531" title="Q182531">battleship <small>(Q182531)</small></a> is also a Wikidata class. All battleships are ships, so <a href="/wiki/Q182531" title="Q182531">battleship <small>(Q182531)</small></a> is a subclass of <a href="/wiki/Q11446" title="Q11446">ship <small>(Q11446)</small></a> as well. Suppose we want to find all subclasses of <a href="/wiki/Q11446" title="Q11446">ship <small>(Q11446)</small></a> that are ship classes in the <i>similar design</i> (<a href="/wiki/Q559026" title="Q559026">ship class <small>(Q559026)</small></a><span class="external_link-reasonator">  <span typeof="mw:File"><a href="https://reasonator.toolforge.org/?q=Q559026&lang=en" title="View with Reasonator"><img alt="View with Reasonator" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/12px-Wikidata-Reasonator_small_logo.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/18px-Wikidata-Reasonator_small_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/24px-Wikidata-Reasonator_small_logo.svg.png 2x" data-file-width="500" data-file-height="500" /></a></span></span><span class="external_link-SQID"> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=Q559026&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></span>) sense. If we just query all subclasses of ships, we will get both <a href="/wiki/Q182531" title="Q182531">battleship <small>(Q182531)</small></a> and <a href="/wiki/Q309336" title="Q309336">Nimitz-class aircraft carrier <small>(Q309336)</small></a>. The former is not what we want: battleships are not all of similar design. </p><p>With metaclasses however, we don't have that problem. We just find all the instances of <a href="/wiki/Q559026" title="Q559026">ship class <small>(Q559026)</small></a> and we have what we want. As <battleship> won't be an instance of <a href="/wiki/Q559026" title="Q559026">ship class <small>(Q559026)</small></a>, that problem is solved. </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Atom_classes.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/6/64/Atom_classes.svg/220px-Atom_classes.svg.png" decoding="async" width="220" height="236" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/64/Atom_classes.svg/330px-Atom_classes.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/64/Atom_classes.svg/440px-Atom_classes.svg.png 2x" data-file-width="747" data-file-height="802" /></a><figcaption>Classification of atoms with classes, like Hydrogen as the class of all Hydrogen atoms, and Elements as a class of class of atoms.</figcaption></figure> <p>This is also relevant in chemistry. For example there are a lot of hydrogen atoms in the universe. Following the token/type principle, Hydrogen would then be a class, all of whose instances are those billions of hydrogen atoms. </p> <dl><dt>Note on the definition of chemical element</dt> <dd>please note that the definition of "chemical element" taken in this example is, for simplicity, "type of atom with a specific number of protons". The definition of element is sometimes a little bit different and can be "substance in which all atoms have the same number of protons" depending on the country or on the chemistry school.</dd></dl> <p>But usually chemists also use the concept of <i>chemical elements</i>. "Hydrogen is a chemical element" is something that teachers can assert. But what is the relationship, then? There is no problem if we decide that chemical element is a class of classes of atoms. It is different than the class of all isotopes of a chemical element as well. If we had only classes and instances, it would be difficult to express the relationship between Hydrogen and chemical elements because we wouldn't have an explicit way to discriminate the different classes of atoms, since both the Hydrogen atoms, atoms of some Hydrogen isotope (i.e., deuterium or tritium), metallic atoms, and so on would all be subclasses of atoms. It's convenient then to classify all those classes into a class of classes that share something. Chemical element classes share something: every one of them contains atoms with the same atomic number. Two different classes of atoms have a different atomic number for their instances. Which is not the case for, let's say the class of all metallic atoms, which groups together atoms some of which have different atomic numbers. </p><p>A class of classes is called a <a href="/wiki/Q19478619" title="Q19478619">metaclass <small>(Q19478619)</small></a><span class="external_link-reasonator">  <span typeof="mw:File"><a href="https://reasonator.toolforge.org/?q=Q19478619&lang=en" title="View with Reasonator"><img alt="View with Reasonator" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/12px-Wikidata-Reasonator_small_logo.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/18px-Wikidata-Reasonator_small_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/24px-Wikidata-Reasonator_small_logo.svg.png 2x" data-file-width="500" data-file-height="500" /></a></span></span><span class="external_link-SQID"> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=Q19478619&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></span>. </p> <div class="mw-heading mw-heading3"><h3 id="Class_of_instances,_class_of_class_of_instances,_..."><span id="Class_of_instances.2C_class_of_class_of_instances.2C_..."></span>Class of instances, class of class of instances, ...</h3></div> <p>It's also possible to repeat the pattern to get <i>higher level metaclasses</i>. These classes are [???]. Some researchers have studied them and have described patterns and antipatterns on Wikidata to help in finding mistakes<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>. </p><p>Some items exist on Wikidata that represent those higher level metaclasses : <a href="/wiki/Q24017414" title="Q24017414">second-order class <small>(Q24017414)</small></a><span class="external_link-reasonator">  <span typeof="mw:File"><a href="https://reasonator.toolforge.org/?q=Q24017414&lang=en" title="View with Reasonator"><img alt="View with Reasonator" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/12px-Wikidata-Reasonator_small_logo.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/18px-Wikidata-Reasonator_small_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/24px-Wikidata-Reasonator_small_logo.svg.png 2x" data-file-width="500" data-file-height="500" /></a></span></span><span class="external_link-SQID"> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=Q24017414&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></span> (an example of such a class is "ship class") ; <a href="/wiki/Q24017465" title="Q24017465">third-order class <small>(Q24017465)</small></a><span class="external_link-reasonator">  <span typeof="mw:File"><a href="https://reasonator.toolforge.org/?q=Q24017465&lang=en" title="View with Reasonator"><img alt="View with Reasonator" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/12px-Wikidata-Reasonator_small_logo.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/18px-Wikidata-Reasonator_small_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/24px-Wikidata-Reasonator_small_logo.svg.png 2x" data-file-width="500" data-file-height="500" /></a></span></span><span class="external_link-SQID"> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=Q24017465&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></span> ; <a href="/wiki/Q24027474" title="Q24027474">fourth-order class <small>(Q24027474)</small></a><span class="external_link-reasonator">  <span typeof="mw:File"><a href="https://reasonator.toolforge.org/?q=Q24027474&lang=en" title="View with Reasonator"><img alt="View with Reasonator" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/12px-Wikidata-Reasonator_small_logo.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/18px-Wikidata-Reasonator_small_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/24px-Wikidata-Reasonator_small_logo.svg.png 2x" data-file-width="500" data-file-height="500" /></a></span></span><span class="external_link-SQID"> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=Q24027474&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></span> ; <a href="/wiki/Q24027515" title="Q24027515">fifth-order class <small>(Q24027515)</small></a><span class="external_link-reasonator">  <span typeof="mw:File"><a href="https://reasonator.toolforge.org/?q=Q24027515&lang=en" title="View with Reasonator"><img alt="View with Reasonator" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/12px-Wikidata-Reasonator_small_logo.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/18px-Wikidata-Reasonator_small_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Wikidata-Reasonator_small_logo.svg/24px-Wikidata-Reasonator_small_logo.svg.png 2x" data-file-width="500" data-file-height="500" /></a></span></span><span class="external_link-SQID"> <span typeof="mw:File"><a href="https://sqid.toolforge.org/#/view?id=Q24027515&lang=en" title="View with SQID"><img alt="View with SQID" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/25px-SQID_logo.svg.png" decoding="async" width="25" height="7" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/38px-SQID_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ed/SQID_logo.svg/50px-SQID_logo.svg.png 2x" data-file-width="179" data-file-height="48" /></a></span></span> ... There are, however, very few known instances of the highest levels<sup id="cite_ref-Cyc_3-0" class="reference"><a href="#cite_note-Cyc-3"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>. </p><p><br /> </p> <div class="mw-heading mw-heading2"><h2 id="Tools_and_properties">Tools and properties</h2></div> <p>The two main properties used in Wikidata to class items subjects are <a href="/wiki/Property:P31" title="Property:P31">instance of <small dir="ltr">(P31)</small></a> and <a href="/wiki/Property:P279" title="Property:P279">subclass of <small dir="ltr">(P279)</small></a>. </p> <ul><li><code>{{<a href="/wiki/Template:Classification" class="mw-redirect" title="Template:Classification">Classification</a>}}</code>, a template.</li> <li><code>{{<a href="/wiki/Template:PropertyForThisType" title="Template:PropertyForThisType">PropertyForThisType</a>}}</code> : a template that lists some property applicable to the instances of some class</li></ul> <div class="mw-heading mw-heading3"><h3 id="Properties_associated_to_a_class">Properties associated to a class</h3></div> <ul><li><code>{{<a href="/wiki/Template:Item_documentation" title="Template:Item documentation">Item documentation</a>}}</code> ; create a list of properties in the item <i>/class</i> subpage (see for example <a href="/wiki/Talk:Q5/class" title="Talk:Q5/class">Talk:Q5/class</a>)</li> <li>Wikidata list</li></ul> <div class="mw-heading mw-heading2"><h2 id="Related">Related</h2></div> <ul><li><a href="/wiki/Special:MyLanguage/Help:Basic_membership_properties" title="Special:MyLanguage/Help:Basic membership properties">Help:Basic membership properties</a></li> <li><a href="/wiki/Q28326461" title="Q28326461">Wikidata property for the relationship between classes <small>(Q28326461)</small></a></li> <li><a href="/wiki/Q28326730" title="Q28326730">Wikidata property for the relationship of the element to its class <small>(Q28326730)</small></a></li></ul> <div class="mw-heading mw-heading2"><h2 id="Notes">Notes</h2></div> <ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><a href="#cite_ref-1">↑</a></span> <span class="reference-text">we will not count robots as Wikimedians ;)</span> </li> </ol> <ol class="references"> <li id="cite_note-2"><span class="mw-cite-backlink"><a href="#cite_ref-2">↑</a></span> <span class="reference-text"><a rel="nofollow" class="external free" href="http://snap.stanford.edu/wikiworkshop2016/papers/Wiki_Workshop__WWW_2016_paper_11.pdf">http://snap.stanford.edu/wikiworkshop2016/papers/Wiki_Workshop__WWW_2016_paper_11.pdf</a></span> </li> <li id="cite_note-Cyc-3"><span class="mw-cite-backlink"><a href="#cite_ref-Cyc_3-0">↑</a></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1377389009">.mw-parser-output cite.citation{font-style:inherit}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .id-lock-free a,.mw-parser-output .citation .cs1-lock-free a{background:linear-gradient(transparent,transparent),url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited a,.mw-parser-output .id-lock-registration a,.mw-parser-output .citation .cs1-lock-limited a,.mw-parser-output .citation .cs1-lock-registration a{background:linear-gradient(transparent,transparent),url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription a,.mw-parser-output .citation .cs1-lock-subscription a{background:linear-gradient(transparent,transparent),url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-ws-icon a{background:linear-gradient(transparent,transparent),url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{font-size:100%}.mw-parser-output .cs1-maint{display:none;color:#33aa33;margin-left:0.3em}.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}</style><cite id="CITEREFFoxvog,_D.2005" class="citation conference cs1">Foxvog, D. (2005). <a rel="nofollow" class="external text" href="https://www.researchgate.net/profile/Douglas_Foxvog/publication/231599269_Instances_of_Instances_Modeled_via_Higher-Order_Classes/links/09e41506d92dd5ffbf000000.pdf?inViewer=0&pdfJsDownload=0&origin=publication_detail"><i>Instances of instances modeled via higher-order classes</i></a> <span class="cs1-format">(PDF)</span>. Workshop on Foundational Aspects of Ontologies (FOnt 2005), 28th German Conference on Artificial Intelligence. Koblenz, Germany. pp. 46–54.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=conference&rft.btitle=Instances+of+instances+modeled+via+higher-order+classes&rft.place=Koblenz%2C+Germany&rft.pages=46-54&rft.date=2005&rft.au=Foxvog%2C+D.&rft_id=https%3A%2F%2Fwww.researchgate.net%2Fprofile%2FDouglas_Foxvog%2Fpublication%2F231599269_Instances_of_Instances_Modeled_via_Higher-Order_Classes%2Flinks%2F09e41506d92dd5ffbf000000.pdf%3FinViewer%3D0%26pdfJsDownload%3D0%26origin%3Dpublication_detail&rfr_id=info%3Asid%2Fwww.wikidata.org%3AUser%3ATomT0m%2FClassification%2Fit" class="Z3988"></span></span> </li> </ol>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1&useformat=desktop" 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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