On Wed, May 28, 2014 at 2:48 PM, Markus Krötzsch
<markus(a)semantic-mediawiki.org> wrote:
David,
Regarding the question of how to classify properties and how to relate them
to items:
* "same as" (in the sense of owl:sameAs) is not the right concept here. In
fact, it has often been discouraged to use this on the Web, since it has
very strong implications: it means that in all uses of the one identifier,
one could just as well use the other identifier, and that it is
indistinguishable if something has been said about the one or the other.
That seems too strong here, at least for most cases.
* In the world of OWL DL, sameAs specifically refers to individuals, not to
classes or properties. Saying "P sameAs Q" does not imply that P and Q have
the same extension as properties. For the latter, OWL has the relationship
owl:equivalentProperties. This distinction of instance level and schema
level is similar to the distinction we have between "instance of" and
"subclass of".
* Therefore, I would suggest to use a property called "subproperty of" as
one way of relating properties (analogously to "subclass of"). It has to be
checked if this actually occurs in Wikidata (do we have any properties that
would be in this relation, or do we make it a modelling principle to have
only the most specific properties in Wikidata?).
* The relationship from properties to items could be modelled with the
existing property "subject of" (P805).
* It might be useful to also have a taxonomic classification of properties.
For example, we already group properties into properties for "people",
"organisations", etc. Such information could also be added with a specific
property (this would be a bit more like a "category" system on property
pages).
Yes. That's the way forward for now.
On the other hand, some of this might coincide with
constraint
information that could be expressed as claims. For instance, person
properties might be those with "Type" (i.e., "rdfs:domain")
constraint
human. By the way, our constraint system could use some systematisation --
there are many overlaps in what you can do with one constraint or another.
I hope to have a team of students work on improving constraints
reports and everything around it later in the year. It'll depend on if
they pick this project though.
Cheers
Lydia
--
Lydia Pintscher -
http://about.me/lydia.pintscher
Product Manager for Wikidata
Wikimedia Deutschland e.V.
Tempelhofer Ufer 23-24
10963 Berlin
www.wikimedia.de
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