*Is there any schema describing all the keys used in
If you mean properties, there's no such schema - any of the properties
existing (see the list here:
can be applied to any of the objects, and any object can have any subset
of the properties. In addition, objects (also called entites) have
labels, descriptions and items also have site links.
It looks like that for each property belonging to
query must be made against the property_Id , so to fetch a human
Yes, to link between properties and IDs you may need to query, though
take a look at this project:
It aims to provide access to property values which already includes labels.
* which API exposes a simple schema 'key' :
'value' , like:
'birth_date' : 'Los Angeles' (similar to what you see at wikidata
See above, this one is probably closest to what you seek. Note that
labels on the properties are not identifiers, they are
language-dependent and can be changed (though in practice this doesn't
happen too often). But if that's what you seek, I think that would be
the best option for you.
* which API expose the value of a relationships
between objects ?
(e.g. Feynman is connected to Cornell University by 'employer'
Properties and relationships are the same.
* Is there a table describing all keys currently
present in wikidata,
so that is possible to know which one to filter ?
Properties are entities too, so techically it's the same table as one
storing entities, but it's probably not useful to you as such. You can
do it in several ways:
: list all
2. This SPARQL query: http://tinyurl.com/hqpwogp
returns list of
properties. You can use SPARQL endpoint
to access the results directly.
3. API at http://queryr.wmflabs.org/about/docs
has /properties which
will provide you with the list of properties.