Abstract: Extremely localized parse rules, dependent only upon either intrinsic characteristics of each packet or upon transitions in characteristics between consecutive pairs or triples of packets, give a determinable fragmentation of an information stream which is relatively insensitive to imbedded error, insertion or deletion. Iterative application of such parsing on the stream of parsed fragments produces a corresponding hierarchy of levels of fragments of increasing length. The highest level fragments are matched to a dictionary or history, tokenized and presented for output to form a compressed data stream.