Re: How to require a Wikidata class or any subclass?

This seems to work (omitting the prefixes for brevity):

start = @<wikidata-organization>

<wikidata-organization> {
  (
    (wdt:P31 [wd:Q43229]; wdt:P31 .*) |
    (wdt:P31 @<subclass_of_organization>; wdt:P31 .*)
  )
}

<subclass_of_organization> {
  (
    (wdt:P279 [wd:Q43229]; wdt:P279 .*) |
    (wdt:P279 @<subclass_of_organization>; wdt:P279 .*)
  )
}

I’m using the truthy statements here instead of the full statements,
because that seems to make more sense to me and it slightly simplifies
the ShEx, but I think the same approach could be made to work with full
statements as well.

Unfortunately, the target class (organization) has to be mentioned
twice, in wikidata_organization and in subclass_of_organization, because
I’m not aware of a way to declare that subclass_of_organization matches
either a specific value or any value with these outgoing arcs. (I guess
that would be a value set on the focus node? Is there such a thing?)

All the triple constraints also mention that other values besides the
required one are fine (the .* parts). I’m not sure why this ugly hack is
necessary, but specifying the predicates as EXTRA doesn’t seem to be
enough. I assume I don’t understand the intricacies of choices well
enough yet :)

Cheers,
Lucas


On 20.06.2018 19:11, Neubert, Joachim wrote:
>
> Hi,
>
>  
>
> In my naive first approach for a „ How to get started with ShEx on
> Wikidata? “ help page [1], I try to verify that every item with a
> certain exernal id is an organization or some subtype of organization.
> With a SPARQL query [2], that is quite straightforward – using a
> property path - and reveals relevant results.
>
>  
>
> However, in ShEx I have not been able to create a query to recursively
> check if an instance is attached to any subclass of a given class. It
> would be great if somebody could help out. My starting point was this [3].
>
>  
>
> Cheers, Joachim
>
>  
>
> PS. While the restriction “some class or a subclass of it” will be
> probably quite common in Wikidata, organization (wd:Q43229) may not be
> the best demo example for an introduction: Currently it has more than
> 19,000 subclasses [4] – often indeed instances. It may however serve
> as a nasty case for tests.
>
>  
>
>  
>
> [1]
> https://www.wikidata.org/wiki/User:Jneubert/How_to_get_started_with_ShEx_on_Wikidata%3F
>
> [2]
> https://www.wikidata.org/wiki/User:Jneubert/Special_queries#PM20_type_%22co/%22_which_are_not_an_organization
>
> [3]
> https://rawgit.com/shexSpec/shex.js/wikidata/doc/shex-simple.html?manifestURL=https://raw.githubusercontent.com/jneubert/wd-shex-test/master/dummy.manifest.json
>
> [4]
> http://zbw.eu/beta/sparql-lab/?endpoint=https://query.wikidata.org/bigdata/namespace/wdq/sparql&queryRef=https://api.github.com/repos/zbw/sparql-queries/contents/wikidata/all_subclasses.rq
>
>  
>