2. A method as in claim 1 , wherein categorization of each provided document by the user-generated input is propagated to all documents within the corresponding stack.
2. A method as in claim 1 , wherein categorization of each provided document by the user-generated input is propagated to all documents within the corresponding stack. 5. A method as in claim 2 , further comprising: defining, by at least one data processor, hierarchical relationships among the plurality of documents within the set of documents; and wherein the grouping algorithms take into account the relationships between documents when grouping the plurality of documents into the plurality of stacks.