@Andra Waagmester: I am a little disconcerted by the property P288 "exact
match" <https://www.wikidata.org/wiki/Property:P2888>. I see it is mostly
used to link entities, not properties, and I can't figure out how it
differs from an external id (unless it's just a convenient way of linking
concepts to databases that do not have an external id in Wikidata?)
On Sat, 22 Sep 2018 at 15:55, Peter F. Patel-Schneider <
pfpschneider(a)gmail.com> wrote:
It is indeed helpful to link the Wikidata ontologies
to other ontologies,
particularly ones like the DBpedia ontology and the
schema.org ontology.
There are already quite a few links from the Wikidata ontology to several
other ontologies, using the Wikidata equivalent class and property
properties.
Going through and ensuring that every class and property, for example, in
the
DBpedia ontology or the
schema.org ontology is the target of a correct (!)
link would be useful. Then, as you indicate, it is not so hard to query
Wikidata using the external ontology or map Wikidata information into
information in the other ontology.
The Wikidata ontology is much larger (almost two million classes) and much
more fine grained than most (or maybe even all) other general-purpose
ontologies. This is appealing as one can be much more precise in Wikidata
than in other ontologies. It does make Wikidata harder to use (correctly)
because to represent an entity in Wikidata one has to select among many
more
alternatives.
This selection is harder than it should be. The Wikidata ontology is not
well
organized. The Wikidata ontology has errors in it. There is not yet a
good
tool for visualizing or exploring the ontology (although there are some
useful
tools such as
https://tools.wmflabs.org/bambots/WikidataClasses.php and
http://tools.wmflabs.org/wikidata-todo/tree.html).
So it is not trivial to set up good mappings from the Wikidata ontology to
other ontologies. When setting up equivalences one has to be careful to
select the Wikidata class or property that is actually equivalent to the
external class or property as opposed to a Wikidata class or property that
just happens to have a similar or the same label. One also has to be
similarly careful when setting up other relationships between the Wikidata
ontology and other ontologies. As well, one has to be careful to select
good
relationships that have well-defined meanings. (Some SKOS relationships
are
particuarly suspect.) I suggest using only strict generalization and
specialization relationships.
So I think that an effort to completely and correctly map several external
general-purpose ontologies into the Wikidata ontology would be something
for
the Wikidata community to support. Pick a few good external ontologies and
put the needed effort into adding any missing mappings and checking the
mappings that already exist. Get someone or some group to commit to
keeping
the mapping up to date. Announce the results and show how they are useful.
Peter F. Patel-Schneider
Nuance Communications
On 9/22/18 4:28 AM, Maarten Dammers wrote:
Hi everyone,
Last week I presented Wikidata at the Semantics conference in Vienna (
https://2018.semantics.cc/ ). One question I asked people was: What is
keeping
you from using Wikidata? One of the common
responses is that it's quite
hard
to combine Wikidata with the rest of the semantic
web. We have our own
private
ontology that's a bit on an island. Most of
our triples are in our own
private
format and not available in a more generic, more
widely use ontology.
Let's pick an example: Claude Lussan. No clue who he is, but my bot
seems to
represented as:
<wdtn:P214
rdf:resource="http://viaf.org/viaf/29578396"/>
<wdtn:P1006 rdf:resource="http://data.bibliotheken.nl/id/thes/p173983111
"/>
Also outputting it in a more generic way would probably make using it
easier
than it is right now. Last discussion about this
was at
https://www.wikidata.org/wiki/Property_talk:P1921 , but no response
since June.
That's one way of linking up, but another way is using equivalent
property (
gender
(
https://www.wikidata.org/wiki/Property:P21) how
it's mapped to other
ontologies. This won't produce easier RDF, but some smart downstream
users
have figured out some SPARQL queries. So linking
up our properties and
classes
to other ontologies will make using our data
easier. This is a first
step.
Maybe it will be used in the future to generate
more RDF, maybe not and
we'll
just document the SPARQL approach properly.
The equivalent property and equivalent class are used, but not that
much. Did
anyone already try a structured approach with
reporting? I'm considering
parsing popular ontology descriptions and producing reports of what is
linked
to what so it's easy to make missing links,
but I don't want to do
double work
here.
What ontologies are important because these are used a lot? Some of the
ones I
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