This page is a proposal to revise and clarify OSM tags related to Wikipedia and related projects. There is a plethora of wikipedia tags in OSM. The 3 most common are wikipedia=*, wikipedia:lang=*, and wikidata=*.
wikipedia=* usually links to an article about the given object -- a one-to-one mapping. For example, a famous building or a country outline links to the building or a country article. The other, less frequent usages should be clarified:
- Wikipedia article is a list of the city library buildings, not the specific library building tagged. The lists' content is more fragile, and should be treated differently from the wikipedia tag. Use wikipedia_list:lang=Article name instead, with the language code as part of the key because the list in one language may or may not include the same information in another. This also means that we might not want to have wikidata_list tag for it (TBD).
- Only a part of a Wikipedia article is dedicated to this OSM object. The tag's value would have a "#" symbol in it. Just like a list, this tag is highly language dependent (a wiki article in another language might dedicate a whole page to this object, or not mention it at all). Instead, use wikipedia_list:lang=Article name#section
- Wikipedia article describes the subject of the location, instead of the location itself. For example, a statue is tagged with the article about the person themselves. Should use subject:wikipedia=* and/or subject:wikidata=*.
- Wikipedia article is about the owner of the chain, e.g. McDonalds, not the specific location. Should use operator:wikipedia=* and/or operator:wikidata=*.
Some OSM object may have a narrower meaning than the Wikipedia article. A parish in England has historical and administrative boundary, with the administrative boundary excluding the city center. Both boundaries are best described by the same Wikipedia article, yet neither is truly a 1:1 match. Some language Wikis may contain separate (often bot-generated) pages for each meaning, but (in this case) English would probably have a single article. It might make sense for these cases to reuse the same wikipedia tag for both, but keep wikidata tag different.
The wikidata=* tag is should be a one-to-one match with the OSM object itself. This means that any time the object is not a perfect match with the Wikidata entity, a different tag should be used.
Sometimes, the same wikipedia and/or wikidata tags exist on a relationship, as well as on some of its members. Per Key:wikipedia guideline, wikipedia (and by extension, wikidata) tags should only be set on the relation, and not on its members.