8. A method of logically identifying document elements in a document image, comprising the steps of: storing a set of at least one predetermined structural model, each structural model defining at least one level of a nested one-dimensional hierarchy of relationships defining separations between document elements of a corresponding model document; identifying major background regions in the document image; defining relationships between the identified major background regions of the document image; converting the defined relationships of the document image into at least one level of a nested one-dimensional hierarchy of relationships by selecting coextensive major background regions extending perpendicular to a direction of each of the at least one level of the nested one-dimensional hierarchy of relationships; selecting a top level of relationships of the at least one level of relationships of the document image as a current document image level; selecting a top level of relationships of the at least one level of relationships for the at least one stored structural model to form a set of current structural model levels; comparing the current document image level to each current structural model level of the set of current structural model levels; selecting each structural model whose current level matches the current document image level to form a set of matching structural models; determining if any additional document image levels exist; if so, selecting a next document image level as the current document image level and selecting a corresponding next level for each of the set of matching structural models as the current structural model level to reform the set of current structural models; repeating the comparing step through the next document image level selecting step until no additional document image levels exist; determining if a single selected structural model exists or a plurality of selected structural models exist; if a plurality of selected structural models exists, selecting a most similar one of the selected structural models that is most similar to the defined relationships of the document image as the single selected structural model; and identifying the document elements of the document image based on logical tags of the single selected structural model.
14. The method of claim 8, further comprising the steps of: determining, after the structural model selecting step, if no structural models were selected; and if so, using the document image to form a new structural model.