The IAB Taxonomy V2 classifier categories texts into 560 topics. It has four levels of depth, a main category (e.g. sports, business or science) and subcategories (soccer, agriculture or physics). It's based on the IAB Quality Assurance Guidelines (QAG) Content Taxonomy V2, released 1 March 2017. The class name has up to 6 parts, separated by underscores: "main topic_sub topic_id1_id2_id3_id4" where the ids are the IAB level ids (use the ids for mapping).