Replace nde:distinctObjectsURI and :distinctObjectsLiteral with void-ext

[ddeboer]

While we do need an nde: prefix for nde:graphUri and nde:subjectFilter, it turns out for nde:distinctObjectsURI and nde:distinctObjectsLiteral an existing vocabulary is already available: http://ldf.fi/void-ext. However, that URL does not resolve but http://akswnc7.informatik.uni-leipzig.de/dstreitmatter/archivo/ldf.fi/void-ext/2020.08.10-180627/void-ext_type%3DgeneratedDocu.html works.

Should we use this existing (but possibly unmaintained) vocabulary or continue to define and use our own?

[coret]

http://ldf.fi/void-ext redirects to http://150.146.207.114/lode/extract?owlapi=true&url=http://ldf.fi/void-ext which gives a 500. The URL http://150.146.207.114/lode/source?url=http://ldf.fi/void-ext does provide the source of http://ldf.fi/void-ext I have contacted SeCo HELP to see if the service can be restored and to ask about maintenance.

[EnnoMeijers]

void-ext is also available at the official archivo list at DBpedia, see https://archivo.dbpedia.org/info?o=http://ldf.fi/void-ext. The ontology is not available through http://onki.fi/en/browser/, my impression is that void-ext is not a well maintained ontology and we should be cautious to use it.

[yoge1]

Thanks for contacting us. void-ext is available via the http://ldf.fi Linked Data publication service - which is run by our research group. The vocabulary is downloadable via its URI http://ldf.fi/void-ext using an appropriate HTTP Accept header e.g. "Accept: text/turtle").

We are using an external LODE service (deployed at https://w3id.org which redirects to http://150.146.207.114) for human-readable documentation for our vocabularies. However, LODE seems to have problems with owl:imports that are not available in RDF/XML format. void-ext owl:imports http://rdfs.org/ns/void which seems to be available only in Turtle format. LODE uses owlapi version 4.0.2 for loading the vocabulary, which throws an exception when trying to read http://ldf.fi/void-ext. (I checked that a newer owlapi version (5.1.2) doesn't have this issue anymore.)

To fix this issue, I changed http://ldf.fi/void-ext to return RDF instead of redirecting to LODE (we should look for an alternative to LODE). I hope this solves your issue!