Delta encoding is a way of storing or transmitting data in the form of differences (deltas) between sequential data rather than complete files; more generally this is known as data differencing. Delta encoding is sometimes called delta compression, particularly where archival histories of changes are required (e.g., in revision control software). Δ ( v 1 , v 2 ) = ( v 1 ∖ v 2 ) ∪ ( v 2 ∖ v 1 ) {displaystyle Delta (v_{1},v_{2})=(v_{1}setminus v_{2})cup (v_{2}setminus v_{1})} This document describes how delta encoding can be supported as a compatible extension to HTTP/1.1. Delta encoding is a way of storing or transmitting data in the form of differences (deltas) between sequential data rather than complete files; more generally this is known as data differencing. Delta encoding is sometimes called delta compression, particularly where archival histories of changes are required (e.g., in revision control software).