New subject: [Wikidata-l] A note on "instance of:Wikipedia disambiguation page"

20 Aug 2014

Hi all,

We have a lot of statements saying that something is an instance of a 
"Wikipedia disambiguation page" (Q4167410). Unfortunately, this kind of 
information says something about a particular Wikipedia article in a 
particular language, and often is not true for other languages. 
Moreover, even if there is a language where the according article is 
marked as disambiguation page, it is still common that the page gives a 
description of a real item.

Example (bad use of instance of:Wikipedia disambiguation page)
==============================================================

https://www.wikidata.org/wiki/Q247819 (VW Polo)

Enwiki (like many languages) has a normal article here that is not a 
disambiguation page. It says "The Volkswagen Polo is a supermini car 
produced by the German manufacturer Volkswagen". That's very different 
from "The Volkswagen Polo is a disambiguation page."

Even Wikipedias where the VW-Polo article is marked as disambiguation 
page do not claim that the thing they are talking about is the 
disambiguation page. For instance, frwiki has the article in 
Catégorie:Homonymie, yet it says:

"Volkswagen Polo est une automobile, de la gamme des polyvalentes, de la 
marque allemande Volkswagen"

Again, it is not said that VW Polo is a disambiguation page, even though 
the page (not the car) is marked as one.

Proper use of instance of:Wikipedia disambiguation page
=======================================================

Now there are also many proper disambiguation pages. They do not have a 
joint concept, other than the ambiguous title in a particular language.

Examples:
https://en.wikipedia.org/wiki/Jaguar_(disambiguation)
and, entertainingly:
https://en.wikipedia.org/wiki/Disambiguation_(disambiguation)

An item that is "instance of:Wikipedia disambiguation page":

* should not have sitelinks to pages that are not disambiguation pages 
(an item can either be about a Wikipedia page or about a car, but these 
should be kept separate),
* should always use the exact page title as the label (because this is 
the real label of the page; the page "Jaguar (disambiguation)" is not 
called "Jaguar" by anybody),
* should hardly have any statements at all, since there is almost 
nothing that you can truthfully say about a group of pages in many 
different languages, and since we want to avoid project-specific 
statements (that's one reason we have badges as part of site links).

Whether disambiguation pages should have more than a single sitelink at 
all is another question. In my view, if we are talking about a "page", 
it is not the same page in French as it is in English (most properties 
that pages could naturally have, such as authors, language, creation 
date, etc. apply to a single page only). However, I can see that it is 
practical to group such pages nonetheless.

Conclusion
==========

It would be nice if somebody could analyse this problem in more detail 
(how many of our "disambiguation page" items have statements that are 
obviously not about a page but about a car make, animal, etc.). We might 
need some manual effort to clean this up (basically, a kind of 
un-merging game).

The immediate conclusion is that we need to be much more careful 
importing this type of information from one Wikipedia, since it is (by 
its very nature) not project-independent and not universal across languages.

Cheers,

Markus