1. A non-transitory computer-readable storage medium having instructions stored thereon, the instructions executable to cause a data processing apparatus to perform operations including: accessing a representation of a document category; accessing a set of documents, wherein each of the documents of the set is associated with a label indicating whether or not the document is associated with the document category; compiling a list of terms, wherein the list of terms includes distinct terms found in the documents of the set; computing information gain of each of the terms, wherein information gain is computed with regard to the document category; sorting the list by ordering the terms based on respective information gain; creating multiple association rules, wherein at least one of the association rules includes a logical conjunction of at least two terms of the list and one or more of the association rules includes at least one of the distinct terms; and performing an association rule analysis that includes performing the following operations with respect to each of the association rules: obtaining categorization results by using the association rule in categorizing each of the documents of the set with regard to the document category; recording the categorization results; and evaluating a precision of the association rule based on the respective categorization results.
13. The non-transitory computer-readable storage medium of claim 1 , wherein the document category is defined with respect to a topic such that documents in which the topic appears are associated with the document category and documents in which the topic does not appear are not associated with the document category.