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 <mar...@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 in the >> 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'' ? >> >> https://www.wikidata.org/wiki/Q17362350 >> >> >> _______________________________________________ >> Wikidata-l mailing list >> Wikidata-l@lists.wikimedia.org >> https://lists.wikimedia.org/mailman/listinfo/wikidata-l >> >> > > _______________________________________________ > Wikidata-l mailing list > Wikidata-l@lists.wikimedia.org > https://lists.wikimedia.org/mailman/listinfo/wikidata-l >
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