universal queries

[gautschr]

I formulated the following query that (should) ask for all resources in Knora (using Postman and POST to https://api.dasch.swiss/v2/searchextended)

PREFIX knora-api: http://api.knora.org/ontology/knora-api/simple/v2#

CONSTRUCT {
?s knora-api:isMainResource true .
}
WHERE {
?s a knora-api:Resource .
}

I retrieved no results. Is there a mistake in the query or is there a reason that such queries aren't allowed and if so, why? I consider such a query as a very useful one to get an idea about the data.

[benjamingeer]

I think this query should return an error message, because it's too broad to be meaningful.

I consider such a query as a very useful one to get an idea about the data.

The DaSCH repository could have billions of resources in it, belonging to thousands of different resource types. Scrolling through a few random resources isn't going to give you an idea of what's in the repository.

For example, there are likely to be millions of knora-api:Region resources, used for different purposes by different projects. Suppose your search results returned all these Region resources first, before returning any other type of resource? You would have no idea what all these regions were used for. You might think that the DaSCH repository contained only regions... but regions of what? You would not know.

To get an idea of what's in the repository, you need an overview of the projects that are hosted by the DaSCH.