10. One or more non-transitory computer-readable tangible media encoding software operable when executed to: access a corpus stored in one or more tangible media, the corpus comprising a plurality of terms; perform the following for each term of one or more terms of the plurality of terms to yield a plurality of parent-child relationships: identify one or more parent terms of the each term according to directional affinity, the plurality of terms comprising the one or more parent terms, the directional affinity being the number of co-occurrence contexts that include two terms, over the number of co-occurrence contexts that include one term; and establish one or more parent-child relationships from the one or more parent terms and the each term; and automatically generate a hierarchical graph from the plurality of parent-child relationships, wherein the automatically generating the hierarchical graph from the plurality of parent-child relationships comprises reducing the hierarchical graph by: identifying a parent-child relationship and a redundant parent-child relationship of the hierarchical graph; and removing the redundant parent-child relationship from the hierarchical graph.
10. One or more non-transitory computer-readable tangible media encoding software operable when executed to: access a corpus stored in one or more tangible media, the corpus comprising a plurality of terms; perform the following for each term of one or more terms of the plurality of terms to yield a plurality of parent-child relationships: identify one or more parent terms of the each term according to directional affinity, the plurality of terms comprising the one or more parent terms, the directional affinity being the number of co-occurrence contexts that include two terms, over the number of co-occurrence contexts that include one term; and establish one or more parent-child relationships from the one or more parent terms and the each term; and automatically generate a hierarchical graph from the plurality of parent-child relationships, wherein the automatically generating the hierarchical graph from the plurality of parent-child relationships comprises reducing the hierarchical graph by: identifying a parent-child relationship and a redundant parent-child relationship of the hierarchical graph; and removing the redundant parent-child relationship from the hierarchical graph. 13. The computer-readable tangible media of claim 10 : the corpus comprising a plurality of documents, the plurality of documents comprising the plurality of terms; and the hierarchical graph representing a catalog of the plurality of documents.