13. The apparatus of claim 12 , wherein the clustering module is further configured to: calculate a similarity score for each one of the plurality of different domains of a document to a corresponding domain of each remaining document of the plurality of documents; calculate an overall similarity score based on the similarity score for the each one of the plurality of different domains for the document to the each remaining document of the plurality of documents; and cluster the document and one or more of the each remaining document of the plurality of documents when the overall similarity score is above a threshold.
12. The apparatus of claim 10 , wherein the domain specific shingling function comprises identifying a plurality of different domains in each one of the plurality of documents based on metadata extracted from the each one of the plurality of documents.