A delta records enough differences to reconstruct a newer version from the expected earlier one. When most data remains unchanged, this can reduce storage or transfer requirements compared with sending another full copy.
Reconstruction depends on having the correct base and complete change information. Version identity and integrity checks are important because applying a patch to the wrong base can produce an invalid result.
ELI5
Think of sending a list of edits to a document instead of sending the whole document again.
For example, if only a few model weights change in the served representation, a patch can describe those positions and their new values while leaving unchanged values alone.
Does a delta work without its base version?
Usually the intended base is required to reconstruct the complete updated data from the differences.
Is delta encoding always smaller?
No. The benefit depends on how much changed and the overhead needed to describe those changes.
