RCS adopts a reverse delta approach for storing multiple versions of a file. For example, assume a file has three revisions, 1.1, 1.2, and 1.3, RCS stores the file as of version 1.3, then, the differences between 1.2 and 1.3, and the differences between 1.1 and 1.2. When a new version is created, say 1.4, the difference between 1.3 and 1.4 is computed and stored, and the 1.3 version is deleted and replaced by 1.4. Explain why RCS does not simply store the initial version (in this case 1.1) and the differences between each successive version.
What will be an ideal response?
The trade-off between reverse deltas and forward deltas is a response time trade-off. In the case of reverse deltas (as
RCS does), the time to retrieve the latest version is the shortest, while time to retrieve the oldest versions is the
longest. In the case of forward deltas, the time to retrieve the initial (oldest) version is the shortest. In most projects,
retrieving the latest version is the most common case. Note that storing reverse deltas increases the time for creating a
new version.
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