28. The volatile or non-volatile computer-readable storage medium of claim 27 , wherein the one or more sequences of instructions, when executed by the one or more processors, cause the one or more processors to perform associating the category with said set of related nodes by: determining a set of connected nodes that are connected to said first node in the graph, each connected node associated with a connected term; for each particular connected node of said connected nodes: determining a particular degree of cross-reference between the particular connected node and said first node; determining whether the particular degree of cross-reference satisfies a particular threshold; in response to determining that the particular degree of cross-reference satisfies the particular threshold, storing the particular connected node as a related node of said set of related nodes.
28. The volatile or non-volatile computer-readable storage medium of claim 27 , wherein the one or more sequences of instructions, when executed by the one or more processors, cause the one or more processors to perform associating the category with said set of related nodes by: determining a set of connected nodes that are connected to said first node in the graph, each connected node associated with a connected term; for each particular connected node of said connected nodes: determining a particular degree of cross-reference between the particular connected node and said first node; determining whether the particular degree of cross-reference satisfies a particular threshold; in response to determining that the particular degree of cross-reference satisfies the particular threshold, storing the particular connected node as a related node of said set of related nodes. 31. The volatile or non-volatile computer-readable storage medium of claim 28 , wherein each particular degree of cross-reference is based at least in part on both: a first frequency by which the connected term for the particular connected node is in a first set of documents associated with the first term; and a second frequency by which the first term is in a second set of documents associated with the connected term for the particular connected node.