14. A computer-readable storage medium having computer-executable instructions for implementing a method of generating a merged document from a first document and a second document, the method comprising: determining whether the first document has a first document identifier, the first document identifier identifying the first document; obtaining the first document identifier if the first document has a first document identifier; determining whether the second document has a second document identifier, the second document identifier identifying the second document; obtaining the second document identifier if the second document has a second document identifier; comparing the first document identifier of the first document with the second document identifier of the second document; performing a conventional merge of the first and second documents to generate the merged document if any of the first and second documents does not have a document identifier; performing a conventional merge of the first and second documents to generate the merged document if the first document identifier of the first document differs from the second document identifier of the second document; and performing an accelerated merge of the first and second documents to generate the merged document if the first document identifier of the first document matches the second document identifier of the second document.
17. The computer-readable storage medium of claim 14 , wherein the method further comprises: adding unique, persistent identifiers to each of the data units of the merged document if any of the first and second documents does not have a document identifier; and adding unique, persistent identifiers to each of the data units of the merged document if the document identifier of the first document differs from the document identifier of the second document.