  Layouts and sub-layouts constitute an important clue while searching a
document on the basis of its structure, or when textual content is
unknown/irrelevant. A sub-layout specifies the arrangement of document entities
within a smaller portion of the document. We propose an efficient graph-based
matching algorithm, integrated with hash-based indexing, to prune a possibly
large search space. A user can specify a combination of sub-layouts of interest
using sketch-based queries. The system supports partial matching for
unspecified layout entities. We handle cases of segmentation pre-processing
errors (for text/non-text blocks) with a symmetry maximization-based strategy,
and accounting for multiple domain-specific plausible segmentation hypotheses.
We show promising results of our system on a database of unstructured entities,
containing 4776 newspaper images.
