What is the tag theory called?

Question

data mining

I remember there was some kind of scientific theory that meticulously analyzes the topic of tags (those that are attached to publications here to facilitate the search). It covered such topics as tags-synonyms, logical queries with intersections, etc. Now something is interested in the topic, but, for the life of me, I can not find it. Tell me please.

Answer 1

Is that what you are looking for by any chance ?