Malleable Coding with Fixed Reuse

Storage area networks, remote backup storage systems, and similar information systems frequently modify stored data with updates from new versions. In these systems, it is desirable for the data to not only be compressed but to also be easily modified during updates. A malleable coding scheme considers both compression efficiency and ease of alteration, promoting some form of reuse or recycling of codewords. Malleability cost is the difficulty of synchronizing compressed versions, and malleable codes are of particular interest when representing information and modifying the representation are both expensive. We examine the trade-off between compression efficiency and malleability cost measured with respect to the length of a reused prefix portion. The region of achievable rates and malleability is formulated as an information-theoretic optimization and a single-letter expression is provided. Relationships to coded side information and common information problems are also established. Index Terms common information, concurrency control, data compression, distributed databases, multiterminal source coding, side information This work was supported in part by the NSF Graduate Research Fellowship, Grant CCR-0325774, and Grant CCF-0729069. J. Kusuma is with Schlumberger Technology Corporation, Sugar Land, TX 77478 USA (e-mail: [email protected]). L. R. Varshney and V. K. Goyal are with the Department of Electrical Engineering and Computer Science and the Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA 02139 USA (e-mail: [email protected], [email protected]). L. R. Varshney is additionally with the Laboratory for Information and Decision Systems. September 4, 2008 DRAFT