19. The method of claim 18 , further comprising: determining a second category related to the first category; and for each association data record comprising a category-article pair identifier associating the first category and an article identifier identifying with the article, storing a second association data record associating the second category and the article identifier identifying the article.
18. A computer-implemented method for category-based search, the method executed by one or more computer systems and comprising: identifying an event comprising a user interaction with an article stored on a storage device of a client device responsive to monitoring user interactions with the client device; identifying an event schema describing a format of the identified event responsive at least in part to an article type of the article, the schema comprising fields based on the article type and fields that describe interactions with the article; identifying a plurality of attributes associated with the identified event that correspond to the fields based on the article type and fields that describe interactions with the article, the plurality of attributes identified responsive to the article and the monitored user interactions; automatically creating at least a first category associated with the article based at least in part on the plurality of attributes; storing an association data record, the association data record comprising a category-article pair identifier associating the first category and an article identifier identifying the article; receiving an implicit search query; causing the implicit search query to be executed on a data store comprising the association data record; and receiving the association data record from the data store.