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
<mar...@semantic-mediawiki.org <mailto: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
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