1. A computer-implemented method for providing default hierarchical training for social indexing, comprising: maintaining articles of digital information for social indexing; specifying a hierarchically-structured tree of topics, which each comprise a label comprising one or more words; identifying constraints inherent in the literal structure of the topic tree; for each topic in the topic tree, creating a topic model that comprises at least one term derived from the words in at least one of the labels; evaluating the topic models for the topic tree against the constraints; and identifying those of the topic models, which best satisfy the constraints.