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Components of the Problem. Compression/Decompression (CD) Data: Set of data that must be shared by compressor and decompressor for correct decompression Subset of “context” Components of the Problem Compression/Decompression Algorithm (CDA) CD Data Management Signaling (CDDMS)
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Components of the Problem • Compression/Decompression (CD) Data: Set of data that must be shared by compressor and decompressor for correct decompression • Subset of “context” • Components of the Problem • Compression/Decompression Algorithm (CDA) • CD Data Management Signaling (CDDMS) • CD Data Update Algorithm (CDDUA) • CDA, CDDMS and CDDUA are attributes of an S-profile
Compression/Decompression Algorithm (CDA) Includes definition of compressed message representation Example: Lempel-Ziv CD Data Compression Algorithm Compressed message Uncompressed message CD Data Decompression Algorithm Decompressed message Compressed message
CD Data Management Signaling (CDDMS) • Signaling Protocol to • Install the CD Data at the compressor and decompressor • Update the CD Data, while maintaining coherency between compressor and decompressor • Includes Checkpoint establishment and Rollback • Provides robustness against message loss, corruption and misordering • Signalling may take place between the compressor and decompressor, and/or involve a D-server • Part or all may not be needed • E.g. If use only preconfigured static data • E.g. If no dynamic CD Data Update
CD Data Update Algorithm Updated CD Data Updating Data CD Data Update Algorithm (CDDUA) Compressor and decompressor must agree on the algorithm if it is implicit Example: Always append Updating Data to CD Data and keep CD Data size constant by deleting oldest entries (FIFO) Another example: LRU