1. A method comprising: receiving a first document of text that is associated with one or more category labels and that includes one or more sequences of one or more words; determining a category label that represents a first category associated with the first document; sampling the one or more sequences to determine a topic and a co-occurrence relationship between the topic and the category label, where a topic represents a subdivision within a category; sampling the one or more sequences to determine a co-occurrence relationship between a sequence in the first document and the topic; and generating a category-topic model that represents the co-occurrence relationships.