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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