TopicalNet micro-topics have, on average, three parents. Some have ten or more because that is how information actually works. If a whole new topic is needed, it is assembled from the relevant micro-topics. The use of micro-topics to classify individual documents is even more subtle. Even a small document typically activates a dozen or more individual micro-topics.
Larger documents can easily activate a hundred or more.
Because micro-topics are so richly interconnected, the ones that are activated by an individual document are also interconnected. After all, the interconnections themselves are the result of noticing these kinds of relationships within tens of millions of documents. In total, each individual document lights up a distinctive pattern of thematic similarities and interconnections within the micro-topic database, some at very high levels, and others at very minute detailed levels. That is what TopicalNet does.