I agree with Peter here. Daniel's statement of "Anything that is a subclass of X, and at the same an instance of Y, where Y is not "class", is problematic." is simply too strong. The classical example is Harry the eagle, and eagle being a species.
The following paper has a much more measured and subtle approach to this question: http://snap.stanford.edu/wikiworkshop2016/papers/Wiki_Workshop__WWW_2016_paper_11.pdf I still think it is potentially and partially too strong, but certainly much better than Daniel's strict statement. On Mon, Jan 9, 2017 at 7:58 AM Peter F. Patel-Schneider < [email protected]> wrote: > On 01/09/2017 07:20 AM, Daniel Kinzler wrote: > > Am 09.01.2017 um 04:36 schrieb Markus Kroetzsch: > >> Only the "current king of Iberia" is a single person, but Wikidata is > about all > >> of history, so there are many such kings. The office of "King of > Iberia" is > >> still singular (it is a singular class) and it can have its own > properties etc. > >> I would therefore say (without having checked the page): > >> > >> King of Iberia instance of office > >> King of Iberia subclass of king > > > > To be semantically strict, you would need to have two separate items, > one for > > the office, and one for the class. Because the individual kinds have not > been > > instances of the office - they have been holders of the office. And they > have > > been instances of the class, but not holders of the class. > > > > On wikidata, we often conflate these things for sake of simplicity. But > when you > > try to write queries, this does not make things simpler, it makes it > harder. > > > > Anything that is a subclass of X, and at the same an instance of Y, > where Y is > > not "class", is problematic. I think this is the root of the confusion > Gerards > > speaks of. > > There is no a priori reason that an office cannot be a class. Some > formalisms > don't allow this, but there are others that do. Some sets of rules for > ontology construction don't allow this, but there are others that do. > There > is certainly no universal semantic consideration, even in any strict > notion of > semantics, that would require that there be two separate items here. > > As far as I can tell, the Wikidata formalism is not one that would disallow > offices being classes. As far as I can tell, the rules for constructing > the > Wikidata ontology don't disallow it either. > > Peter F. Patel-Schneider > Nuance Communications > > _______________________________________________ > Wikidata mailing list > [email protected] > https://lists.wikimedia.org/mailman/listinfo/wikidata >
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