and the class of items that can have <occupation:politician> should be
'person' not 'human'. 'person' as defined by VIAF could include
Stubbs the
cat-with-a-name, as well as fictional humans etc. so Stubbs would be
<instance of:cat with a name> which would be <subclass of:person> and
<subclass of:cat>
or maybe Stubbs <instance of:cat> and <instance of:non-human politician>.
or maybe the constraint should be property 'occupation' has <domain:person>
and <domain:Stubbs>. Yeah I like that last one best.
I think the difference between 'occupation' and 'profession' is that if a
cat can do it then it's an 'occupation'.
Yes the class tree needs work, especially the higher levels, and copying
someone else's High Level Ontology seems to be impractical as they all seem
to be copyrighted. I hope that this is the kind of thing that will get
better with time. We will see.
Joe
On Thu, Aug 27, 2015 at 12:07 AM James Heald <j.heald(a)ucl.ac.uk> wrote:
On 26/08/2015 23:35, Svavar Kjarrval wrote:
On mið 26.ágú 2015 19:24, Joe Filceolaire wrote:
Every other ontology mixes humans with fictional characters and with
groups of humans and possibly fictional humans (biblical characters
for instance). Wikidata has gone to a lot of trouble to try to
untangle these into separate classes. Anyone trying to get an
exhaustive list of humans and not using <instance of:human> deserves
everything he gets.
P21 (sex or gender) is very explicitly specified as being usable for
humans and for other creatures. At the request of some languages we
have separate items for 'female human' and for 'female creature' (we
have the same for male), 'Female human' is 'subclass of:female
creature'. Relying on P21 to tell if something is or is not human is
not recommended as it will probably miss out all the humans who are
neither male nor female - wikidata has about a dozen other values that
can be used with this property.
Father (P22) and mother (P25) can perfectly well be used for
non-humans and if the current constraints on these properties flag
this as a problem then the constraints will have to be updated. I
expect to see extensive pedigrees for racehorses entered in Wikidata.
Note that there is a proposal under consideration to replace P22 and
P25 with a single 'parent' property.
Hope this helps
Joe
For me, it doesn't help. One of the purposes of Wikidata is that it
should also be machine readable. If I were trying to, for example,
travel recursively through the declarations to find deep common facts
about some group of items, it would take much more work than necessary
if I have to hunt down and code around a lot of wrongly categorised
trees and special cases in the data structure.
One other example is Stubbs, the current mayor of Talkeetna, (Q7627362)
which happens to be a cat. The Wikidata item for Stubbs has the
declaration P31->Q146 (cat). However, it also has the definition
P31->Q30185 (mayor), a subclass of Q2285706 (head of government) which
is a subclass of Q82955 (politician) and that's finally a subclass of Q5
(human). One might suggest that since the item for Stubbs is
specifically declared as a cat, that definition has priority (or some
variation of that logic). The problem is that a machine cannot
automatically understand that. Without special programming and/or a way
to define contradictions like that in Wikidata, both facts are assumed
to be correct. The machine might not even know that there is a
contradiction at all so the machine, in its inferences, will assume
Stubbs is both a human and a cat.
- Svavar Kjarrval
There are a *lot* of problems with P279 (subclass), right across Wikidata.
These will only be corrected once people start doing searches in a
systematic way and addressing the anomalies they find.
In this case, politician (Q82955) should *not* be a subclass of human
(Q5), instead it should be a subclass of something like occupation
(Q13516667), or alternatively perhaps profession (Q28640).
My understanding is that currently there are a vast number of incorrect
subclass relationships in the project, messing up tree searches, and so
far it is something that has simply not yet been systematically addressed.
-- James.
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