However, there is another way:
publishing a SPARQL endpoint for RDF data that conforms to commonly used ontologies and which is self documenting using VoID.
Here's a list of very common ontologies, so much so they are part of the RDFa Core Initial Context: https://www.w3.org/2011/rdfa-context/rdfa-1.1
And here's a description of how to use VoID: https://www.w3.org/TR/void/
Bonus— @bobdc 's post on exploring unknown sparql endpoints: https://www.bobdc.com/blog/exploring-a-sparql-endpoint/