Ontology is the knowledge of relations between subjects.
2022-03-23 on matrix
I once published a review of most common categorization systems in Russian:
I found 7 different types of such systems
In short, translated:
#tags like this, one might call them hashtags
Metatags?
Classic wiki categories
Forward indices
Hierarchy
Map of content
None
I didn't find any more categorization systems. Everything is a mixture between the seven
There's no distinction between linking to the topic and inclusion in the topic with the link+backlink combo