1. A computer implemented method of generating a small update package adapted to enable an update of an old version of content to a new version of content, the method comprising: (i) obtaining a conversion element and a delta, said delta comprising update commands, wherein the commands are associated with data entries, wherein both versions are storable on a computer readable storage device and comprise items and reference items which are items that comprise a reference to another item or address, wherein at least some of the update commands are further associated with the reference items such that the reference in the items are changed by the update commands during the update, said conversion element comprising a plurality of shift rules, wherein said shift rules reflect shifts of items in the new version in view of their position in the old version, wherein the shift rules are set such that applying the shift rules on references of reference items in the old version yields a prediction of corresponding reference items in the new version and further yields a prediction of corresponding data entries in the delta; (ii) generating a small delta that includes modified data entries, the generation of said modified data entries comprising: a) applying said shift rules of said conversion element on the reference items of said old version, said reference items corresponding to data entries in said delta, giving rise to converted old items; and b) generating said modified data entries by computing distances between said data entries of said delta and corresponding converted old items; and (iii) generating said small update package by associating said conversion element with said small delta, wherein said generating further comprises compressing said small delta, giving rise to said small update package, wherein the compressing comprises compressing said conversion element; and (iv) outputting said small update package.