1. A method for structuring a legacy document comprising a part of a homogeneous collection from an input document format to a structured document format more useful for document structure analyses comprising: fragmenting the document into a plurality of document content elements in accordance with a predetermined set of document attributes identifiable from the input document format; clustering selective sets of the content elements having document attribute similarities; validating the clustered sets with reference to common textual properties and organizational content within the collection; categorizing the clustered sets into predetermined categories comprising structured elements of the structured document format; and organizing the document content elements by hierarchical dependency from the predetermined categories, wherein the organized document elements comprise the desired structured document format.