case above is different than cathegories in the article you link. U can can use overpass and get all paths in south wales but no query will get you seven summits. I believe this is valid relation. Just dont know how to tag it.
They kind of have a point though: That page’s main argument against category relations is that you can use a query instead. That’s not the case with any of the various “Seven Wonders”, for example. (Although the Seven Summits could be identified using an overpass query.)
Then again, one problem with “The best X” style lists is that they are somewhat arbitrary. For example, the “Seven Wonders of the Industrial World” are not really an agreed upon concept as far as I know, but mostly the creation of British TV. So we are kind of getting into “the best hiking routes according to Foobar Guide” territory here.
Yes, “Seven Wonders” seems to be an subjective list created by the BBC. The topics which the TV series treats should be added into Wikidata. I don’t think that we should add those kind of informations into OSM.
I really think that this kind of data will be a nice way to enhance OSM functionality. I totally agree with arguments on categories. We do not want “Best clubs in London” relations, really. But in the same time i have a feeling that we miss some opportunity here to add valuable information to the map. If not relations - what?
As far as i underestand Wikidata does not include geolocation. Do i miss sth?
It’s something that was discussed at length in the German OSM community, particularly the forum. Have a read of that to get both sides of the topic.
There’s no hard-and-fast rule, but generally speaking, if you can get the information you need from e.g. Overpass, there’s no need to create a relation. In the case of the “Struve Geodetic Arc”, it would seem that tags on the constituent observatories would make sense. I’d have a look at how other UNESCO World Heritage Sites are mapped, and see if you can get anything useful from there, and of course ask the people who mapped the things already in OSM, such as https://www.openstreetmap.org/way/37558758 for their opinion too.