1. A method of incrementally processing structured documents, the method comprising: receiving partial data of one of a plurality of structured documents, wherein each of the documents comprises a plurality of elements that define a hierarchy; identifying which of the structured documents is associated with the partial data; determining which of the elements of the document are included in the received partial data; determining a position of each of the received elements in the hierarchy; identifying a specified portion of the document, said specified portion comprising at least one of the received elements; generating an isomorphic digest value based on the specified portion, wherein the isomorphic digest value comprises a cryptographic hash value based on the specified portion of the document; providing, for processing, the isomorphic digest value, the received elements and the position of each of the received elements in the hierarchy; and identifying data associated with at least one other document based on the isomorphic digest value.