5. The method of claim 1 , wherein the identifying comprises: gathering nodes in the weighted graph into one or more clusters of strongly inter-connected nodes; and identifying document images represented by nodes in a same cluster as documents sharing common underlying structures.
5. The method of claim 1 , wherein the identifying comprises: gathering nodes in the weighted graph into one or more clusters of strongly inter-connected nodes; and identifying document images represented by nodes in a same cluster as documents sharing common underlying structures. 8. The method of claim 5 , further comprising: identifying a representative document image for the one or more clusters; indexing the representative document images in a classification index; and labeling documents sharing common underlying structures in a second plurality of document images by searching the second plurality of document images in the classification index for similar document images.