The Tao of Topic Maps (2000)
ontopia.net
ontopia.net
As for the usefulness of the Topic Maps, Mind Maps and ontologies in general... they are useful instantly for the person who composes them as a way to organize thoughts. Pretty much what Notion, Evernote etc are doing, but with much less elegance.
They are utterly useless as a way to share knowledge.
Also, even 20 years ago, the field was full of old farts wasting everyone's time and consuming salaries. I doubt it changed for better.
How so? Facebook's graph is implemented as a a triplestore where the edges have values rather than entity-relationship of traditional DBMS. GraphQL also exists.
Maybe RDF and getting humans to structure their statistics, transactions, memories, and annotated knowledge rigidly and methodically in a universally-composable manner was a "failure", but now LLMs have the potential to transform freeform content such as from web pages or APIs for us automatically in both materialized and presentation forms that would be mechanically-consumable.
Topic maps truly provide a straightforward organizational metaphor. The foundational topic maps concept —comprising topics, occurrences, and associations— achieves a balance between simplicity and clarity while offering sufficient structure. This allows you to effectively translate your mental model of a domain into a corresponding topic map representation.