Data synchronization

Data synchronization is the process of establishing consistency among data from a source to a target data storage and vice versa and the continuous harmonization of the data over time. It is fundamental to a wide variety of applications, including file synchronization and mobile device synchronization e.g., for PDAs. Synchronization can also be useful in encryption for synchronizing Public Key Servers.

There are tools available for file synchronization, version control (CVS, Subversion, etc.), distributed filesystems (Coda, etc.), and mirroring (rsync, etc.), in that all these attempt to keep sets of files synchronized. However, only version control and file synchronization tools can deal with modifications to more than one copy of the files.

Several theoretical models of data synchronization exist in the research literature, and the problem is also related to the problem of Slepian–Wolf coding in information theory. The models are classified based on how they consider the data to be synchronized.

The problem of synchronizing unordered data (also known as the set reconciliation problem) is modeled as an attempt to compute the symmetric difference ${\displaystyle S_{A}\oplus S_{B}=(S_{A}-S_{B})\cup (S_{B}-S_{A})}$ between two remote sets ${\displaystyle S_{A}}$ and ${\displaystyle S_{B}}$ of b-bit numbers. Some solutions to this problem are typified by:

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