What Does Query-Based Classification Mean? 

For query-based classification, documents are assigned to the categories of a taxonomy using search queries. If a document corresponds to a search query, it is assigned to the category in question. A search query can consist of a single word or a combination of words that are linked with the Boolean operators AND and OR (see What is a Query-Based Taxonomy?).

Since a taxonomy has a hierarchical structure, the categories at the top of the hierarchy contain more general information than the categories in the subordinate levels. The deeper you navigate in the taxonomy, the more specific the information. The search queries are handled by the system accordingly – in order for a document to be classified into a category, it must also match the search queries of all superordinate categories. This means that a document is only classified into a specific category if it would also fit into all superordinate, more general categories.

In contrast with example-based classification, query-based classification does not allow for the graduated similarity of documents to categories. This is because a document either contains the search string and can be classified into a particular category, or it does not.

See also

What is a Query-Based Taxonomy?