1. A method of processing a corpus of electronically stored documents, comprising the steps of: expanding a focus set comprised of at least one initial metadocument, representative of a plurality of documents, into a plurality of subsequent metadocuments, a number of said subsequent metadocuments being approximately equal to a predetermined maximum number, said subsequent metadocuments being descendants of said at least one initial metadocument in a tree, said expanding step comprising, choosing a metadocument in the focus set that represents the most individual documents, and expanding the chosen metadocument into its descendant metadocuments; and clustering the subsequent metadocuments into a predetermined number of new metadocuments. the predetermined number of new metadocuments being less than the predetermined maximum numbers; and selecting the predetermined maximum number so that said expanding and clustering steps can be completed within a time constraint.