(As the What topics can I ask about here? help page doesn’t list what is on-topic here, and the answers I found on Meta are rather broad, I’m not sure if, or to which extent, questions of the following kind are welcome here.)
Would it be on-topic to ask for an RDF vocabulary/ontology?
"How could I annotate my weather data?" (where the OP describes/shows their Open Data and looks for suitable RDF vocabularies to annotate it)
"Is there an ontology that models xy?" (where the OP is not looking only for a vocabulary of properties/classes, but also defined OWL constraints)
"Vocabulary that defines URIs for each character from Studio Ghibli works?" (here the OP is not looking for properties to annotate their data about the characters, but simply for URIs they could use to unambiguously identify the characters, e.g. for
owl:sameAs; so here the corresponding data about the characters is not necessarily required to be open itself, as the OP is not interested in the data, only the URIs)
I’m not sure how to interpret open in these case.
Is a vocabulary Open Data when its documentation is openly licensed, or when its publicly available, or simply when the authors allow others to use their vocabulary URIs (even if the vocabulary documentation/RDF itself is not openly licensed) (but would it even be possible for bare URIs to be non-open)?
Or would it be a side-question (similar to questions about tools), i.e., looking for vocabularies (if open or not?) to annotate your own Open Data?
The typical use case only requires to a) access the documentation/RDF (but not to republish/reuse it) and b) to re-use the URIs defined in this documentation/RDF.