I guess number of instances works in more cases, for example the number of iphone ever built could work ... actually if I look at the ''Population'' article in frwiki, I get "Une *population* est un ensemble d'individus ou d'éléments partageant une ou plusieurs caractéristiques qui servent à les regrouper." (a population is a set of individuals or elements sharing one or several characters that allows to regroup them", this seems another word for "class" :) So I guess it's just a matter of vocabulary.
I guess the population of earth is the number of instances of the "human on earth" class :)
On the other hand, human population is kind of a natural property for a country, its number of wolfes for example may not be worth having a property. Having an item "French Wolf" with a property "number of instances" is way more convenient and generic, and could avoid the burden of having to create (potentially a big number of) properties for each kind of animals we might want to store population in some places.
2015-04-29 21:19 GMT+02:00 Markus Krötzsch markus@semantic-mediawiki.org:
Ok, sounds reasonable.
In all of these cases I do wonder though why we need to store the number at all. We can just count the instances, can we not? Queries allow for this (and will be an official feature in due course).
And in cases where not all instances are supposed to be on Wikidata, there are usually better ways to store the number, e.g., "population of Earth" is better than "number of instances of living person" (besides the fact that we don't have "living person").
Regards,
Markus
On 29.04.2015 20:29, Thomas Douillard wrote:
Actually, like it is, there is no /number of planets/ property, there is a class of planet (solar system planet) together with a /number of instances/ property. This might save us : we can have two item :
- solar system planet (old style definition) and
- solar system planet (new style definition) This might just put the problem in another place though :) although
this might not change the correctness of statements like /<solar system/> <has part> </solar system planet/ (old style)> :)
Pluto can still be an old style definition planet, and maybe <solar system planet> is a subclass of </solar system planet/ (old style)>
Thinking about it, classes are naturally a good way to deal with definitions.
2015-04-29 19:35 GMT+02:00 Markus Krötzsch <markus@semantic-mediawiki.org mailto:markus@semantic-mediawiki.org>:
Hi, General case first: Many statements depend on time and have an end date (e.g., population numbers). The general approach there is to (1) have a qualifier that clarifies the restricted temporal validity and (2) make the current statement "preferred". So your idea with the ranks was a good starting point, but it should be "normal" and "preferred" instead of "deprecated" and "normal". And infovarius was also right in this sense to use a temporal quantifier. Note that more than one statement can be preferred if more than one is current (this could be relevant, e.g., for the classes that Pluto is/was an instance of). However, this answer is only about the general pattern of dealing with things that changed over time, and the intended use of ranks in this case. Things might be different here. It's a special case in that it was not so much the world that changed but the definition, so the real question is what our property "number of planets" really means: (1) "Number of planets at a given time (given as a qualifier), based on the definition of planet adopted at this time" (2) "Number of planets according to the definition that was used when the property was introduced" (3) "Number of planets according to the definition that is current right now" (3) is problematic since it means that the meaning of the property would change over time, and statements that were true will become false. I would strongly discourage this. But both (1) and (2) are possible. If one wants to use (1) then *every* statement with this property must have some time qualifier -- otherwise it will not make any sense since one would not know which definition is meant. In case (2), the number of planets of our solar system is 8, and nothing else. It has never been 9 *according to the definition of planet used by this property*. So if this interpretation is adopted, then the statement with value 9 should really at best be there in a deprecated form, not in a temporal form. It could make sense to keep a deprecated form to warn other users that this should not be reintroduced. One could also add more options, e.g., one could have a qualifier that specifies the definition of planet that is used. This would be a bit like (1) but instead of time one would now always need to specify a definition, and the statements would not be temporal at all (the number would always remain 9 according to the old definition). One could still use "preferred" to mark the statement that is based on the most common definition. The world is beautifully complicated, isn't it? I'll leave it to you experts to discuss what makes sense here here :-) Best regards, Markus On 29.04.2015 18:05, Thomas Douillard wrote: Hi, a small question about qualifiers and ranks. It is well known that the number of planets changed in 2006. Or did it ? Of course, Pluto is still here, it's just its status that changed. The definition of planets changed in 2006. This imply that (imho), the statement "the number of planets inthe solar system in 9" should be deprecated. But infovarius did not agree with me and changed the rank of the claim back to normal and put an end date. I still think it should be deprecated, but it raise me a question: How are we supposed (if we are) to express an information about a deprecation ? Should we include something about the deprecation in the sources ? Should we have a qualifier ''deprecation date'' ?
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